The plaintiff, John N. Adriani, appeals from the judgment of the trial court dismissing his appeal from a decision of the named defendant, the commission on human rights and opportunities (commission). The commission had dismissed the plaintiffs employment discrimination complaint without a hearing on the basis of its finding that there was no reasonable cause to believe that a discriminatory practice had been committed by the plaintiffs employer. Because we conclude that the trial court improperly denied the plaintiff the opportunity to present evidence extrinsic to the record, we remand the case for further proceedings.
On January 20,1988, the plaintiff resigned his position as a buyer for the defendant, the United Illuminating Company (UI), after he had been given the choice of either resigning or being fired. The plaintiff had been employed by UI since September, 1969. On April 14, 1988, the plaintiff filed a complaint with the commission alleging that UI had violated his rights under General Statutes § 46a-60 (a) (1)1 by discriminating against *310him on the basis of his physical disability, hypertension. The plaintiff specifically asserted that, after learning that he suffered from hypertension, UI did not make a reasonable effort to accommodate his condition by transferring him to another available position within the company. Pursuant to General Statutes § 46a-83,2 the investigator for the commission conducted an extensive inquiry concerning the matter and recommended that the plaintiffs complaint be dismissed for lack of reasonable cause. On October 26,1989, the commission dismissed the complaint. The plaintiff filed a request for reconsideration of the dismissal of his complaint, and the commission subsequently denied the request.
On February 2,1990, the plaintiff, pursuant to General Statutes § 46a-94a, filed an appeal in the Superior Court from the commission’s dismissal of his complaint and its denial of his request for reconsideration.3 At the first hearing on this matter, the trial court denied the plaintiffs motion to supplement the record by introducing extrinsic evidence in order to prove alleged procedural irregularities in the commission’s disposition *311of his case. The trial court subsequently dismissed the plaintiffs appeal, concluding that there was substantial evidence in the record to support the investigator’s finding, adopted by the commission, that there was no reasonable cause to believe that UI had committed a discriminatory act in violation of § 46a-60 (a) (l).4 The plaintiff appealed to the Appellate Court, and we transferred the matter to this court pursuant to Practice Book § 4023.
On appeal, the plaintiff claims that the trial court improperly: (1) concluded that there was substantial evidence to support the commission’s finding that there was no reasonable cause for believing that UI had discriminated against the plaintiff on the basis of a physical disability; and (2) refused to allow the introduction of evidence outside the record to support the plaintiff’s claim of procedural irregularities at the agency level.
I
Before addressing the plaintiff’s claim that the trial court should have reversed the commission’s finding of no reasonable cause, it is necessary that we review the facts pertinent to this issue. In 1980, the plaintiff was promoted to a position as a buyer in the purchasing department at UI. The plaintiff’s performance evaluation for the latter half of 1985 rated him as good overall, but noted some reservations about the plaintiff’s attitude toward his job. His 1986 year end evaluation noted significant problems in the plaintiff’s performance, which was rated as marginal overall. The report *312did note that the plaintiff’s attitude toward his work had improved toward the end of the year, but it also stated that termination was possible if the plaintiff did not continue this improved performance. The 1987 year end evaluation, which was given to the plaintiff by his supervisor, James Nesdale, on December 14,1987, outlined continuing problems with the plaintiff’s performance, and stated that “[i]t is now totally up to [the plaintiff] to effect an immediate and lasting correction of all deficiencies. Failure to do so will result in a recommendation being made for his termination.” Nesdale also claimed that, at the time he gave the plaintiff this evaluation, he also gave verbal notice that he would be fired unless his performance improved within the next thirty days. The plaintiff denies that Nesdale ever made such a statement.5
The plaintiff took a medical leave of absence from his job from December 14,1987, to December 29,1987, because of high blood pressure. That same month, the plaintiff, on the advice of Nesdale, sought professional counseling with UI’s employee assistance program, which in turn referred him to John Dolan, chairman of the psychiatry department at St. Vincent’s Medical Center. On or about January 7,1988, William Manniel, manager of training and development for UI, received a letter from Dolan concerning the plaintiff. The letter stated that, largely as a result of a personality clash between the plaintiff and his supervisor, the plaintiff suffered from hypertension and that this condition had become more serious in recent months. Dolan “strongly” recommended that the plaintiff be transferred to another job within UI.
*313The plaintiff claims that he was told by Manniel shortly thereafter that, because of Dolan’s letter, UI considered him a “medical liability” and that this condition could result in his termination. Manniel denied that he made any such statement. He claimed, rather, that he told the plaintiff that efforts were being made to find him another position within the company, but that his past performance significantly hurt his chances for obtaining a transfer. Manniel contended that he told the plaintiff that he would have to be fired if a transfer was not possible because he could not remain in his present position as a buyer. The plaintiff also claims that in early January, 1988, Nesdale “brushed off” his inquiry about an opening in another department and told him that there now was no chance that he would ever be transferred. On January 20, 1988, the plaintiff resigned after being told that he would be terminated if he did not do so. The parties dispute whether, after receiving Dolan’s letter, UI made reasonable efforts to accommodate the plaintiff by trying to transfer him to another position in the company. Specifically, the availability of certain positions, as well as the plaintiff’s qualifications for such positions, are contested.
General Statutes (Rev. to 1987) § 46a-83 (a) provides that “[a]fter the filing of any discriminatory practice complaint, the chairman of the commission shall refer the same to a commissioner or investigator to investigate and if the commissioner or investigator determines after the investigation that there is reasonable cause for believing that a discriminatory practice has been or is being committed as alleged in the complaint, he shall endeavor to eliminate the practice complained of by conference, conciliation and persuasion.”6 If *314the commissioner or investigator finds that there is “reasonable cause” to believe that a discriminatory act has been committed and the complaint is not settled through the procedures outlined in § 46a-83, the complainant is entitled to a hearing on the matter. General Statutes § 46a-84. The plaintiff claims that UI discriminated against him on the basis of his hypertension by refusing to consider transferring him to another department after receiving the letter from Dolan.7 UI asserts, to the contrary, that the plaintiff was fired because no positions were available outside his department and it concluded that it could not allow the plaintiff to return to his job as a buyer. UI also contends that the timing of its decision was motivated by its having decided to terminate the plaintiff by the end of January, in any event, due to performance problems.
We first note the limited scope of review to be exercised by the trial court in reviewing a determination that there is no reasonable cause to believe that a discriminatory practice has been committed. “Judicial *315review of an administrative agency decision requires a court to determine whether there is substantial evidence in the administrative record to support the agency’s findings of basic fact and whether the conclusions drawn from those facts are reasonable.” Connecticut Light & Power Co. v. Department of Public Utility Control, 216 Conn. 627, 639, 583 A.2d 906 (1990); Board of Education v. Commission on Human Rights & Opportunities, 176 Conn. 533, 538, 409 A.2d 1013 (1979). The substantial evidence standard is satisfied if the record provides a “ 'substantial basis of fact from which the fact in issue can be reasonably inferred. . . .’ ” Lawrence v. Kozlowski, 171 Conn. 705, 713, 372 A.2d 110 (1976), cert. denied, 431 U.S. 969, 97 S. Ct. 2930, 53 L. Ed. 2d 1066 (1977).
Before we can apply the substantial evidence test, however, we must resolve the parties’ conflicting contentions about the nature of the reasonable cause determination. The plaintiff contends that in making this determination, the investigator, and the commission when reviewing the investigator’s recommendation, may consider all of the evidence gathered, but the focus of the inquiry should be on the complainant’s representations concerning the alleged discrimination. Moreover, the plaintiff asserts that the commission is not entitled to draw inferences or make credibility determinations that would bear upon disputed material facts. The defendants, however, contend that the commission is allowed not only to consider all the evidence gathered, including that unfavorable to the complainant, but also to make findings concerning material issues of fact by drawing inferences and weighing the credibility of witnesses. We agree with the defendants.
In Ierardi v. Commission on Human Rights & Opportunities, 15 Conn. App. 569, 546 A.2d 870, cert. denied, 209 Conn. 813, 550 A.2d 1082 (1988), the Appellate Court addressed this specific issue. That court rejected *316the claimant’s contention that the reasonable cause standard set forth in § 46a-83 is akin to the concept of a “prima facie case,” which applies to the complainant’s initial burden of production at an adjudicative hearing. Id., 579. The court concluded that “the term ‘reasonable cause’ as used in the statute is synonymous with ‘probable cause.’ Cf. State v. Wilson, 153 Conn. 39, 41, 212 A.2d 75 (1965) (‘reasonable grounds to believe,’ as used in General Statutes § 6-49 [now § 54-lf (b)] is to be equated with ‘probable cause.’) Probable cause ‘ “is a bona fide belief in the existence of facts essential under the law for the action and such as would warrant a man of ordinary caution, prudence and judgment, under the circumstances, in entertaining it.” ’ (Emphasisadded.) Ledgebrook Condominium Assn., Inc. v. Lusk Corporation, 172 Conn. 577, 584, 376 A.2d 60 (1977), quoting Wall v. Toomey, 52 Conn. 35, 36 (1884). ‘Probable cause is a flexible common sense standard. It does not demand that a belief be correct or more likely true than false.’ Three S Development Co. v. Santore, 193 Conn. 174, 175, 474 A.2d 795 (1984). It deals with probabilities, and the ‘application of the factual and practical considerations of everyday life on which reasonable and prudent men act.’ State v. Wilson, supra.”8 Ierardi v. Commission on Human Rights & Opportunities, supra, 580-81.
We conclude, as did the Appellate Court in Ierardi, that the reasonable cause standard requires the commission to consider all reliable probative evidence, *317including evidence unfavorable to the complainant’s claim. In support of this conclusion, the Ierardi court noted that one of the purposes of the reasonable cause determination is to protect respondents from having to go through the hearing process in cases where the complaint is baseless. Id., 580, citing Waterbary v. Commission on Human Rights & Opportunities, 160 Conn. 226, 235, 278 A.2d 771 (1971). In addition to promoting one of the purposes of the reasonable cause finding, this conclusion is also consistent with the principle that we must “make every effort to construe a statutory scheme as a consistent whole.” Powers v. Ulichny, 185 Conn. 145, 149, 440 A.2d 885 (1981); 84 Century Limited Partnership v. Board of Tax Review, 207 Conn. 250, 265, 541 A.2d 478 (1988). The provisions of § 46a-83 (c)9 allow the commission to issue subpoenas for the production of all relevant evidence and, therefore, contemplate that the commission would consider any reliable information pertinent to a complaint, whether that evidence supports the complaint or casts doubt upon it. Ierardi v. Commission on Human Rights & Opportunities, supra, 581.
We conclude that a necessary corollary to allowing the commission to consider all relevant evidence gathered during the investigation is that in making the reasonable cause determination, the investigator, and the commission when reviewing the investigator’s recommendation, are entitled to make findings on disputed issues of material fact by weighing the credibility of the witnesses and drawing inferences.10
*318The facts of the present case provide a clear illustration of why such a result is necessary “to guard against subjecting a respondent to a hearing upon every complaint which might be made to the commission, however unfounded.” Waterbury v. Commission on Human Rights & Opportunities, supra. In his complaint, the plaintiff asserted that Manniel told him that as a result of Dolan’s letter, UI considered him a “medical liability” and that this condition could result in his being terminated. The issue of whether this statement actually was made is a material fact in this case, which, under the plaintiff’s formulation of the reasonable cause determination, could not be decided by an investigator. The inevitable result of the plaintiff’s position is that any claimant can guarantee that he obtains a hearing simply by alleging in his complaint the existence of direct or overt evidence of discrimination. Such a result would encourage unfounded allegations of overt discrimination, thereby requiring a hearing and effectively rendering the reasonable cause determination a nullity.
Even in the absence of claims of overt discrimination, only in the rare case would there be no issues of material fact concerning a discrimination claim. In the present case, for example, the availability, at the time of the plaintiff’s termination, of one of the positions to which he sought to be transferred was a disputed issue of material fact. Under the plaintiff’s view, the investigator would not be allowed to make a finding on that issue. In light of the fact that § 46a-83 contemplates that an investigator will examine all the relevant evidence and the likelihood that material issues of fact will remain after an investigation, we conclude that the investigator must be entitled to resolve such issues if the reasonable cause determination is to serve any practical purpose.
*319We note, however, that the power of the commission, through its investigators, to make findings of material fact as part of the reasonable cause determination, and the trial court’s obligation to review such findings under the substantial evidence standard, is conditional upon the commission having conducted a thorough investigation of the claim and having relied only upon reliable, probative evidence in making those findings. In undertaking its investigation, the commission is obligated to pursue evidence corroborating, as well as contradicting, the plaintiff’s complaint. Such an inquiry was made in this case, where the investigator examined forty-seven items of documentary evidence and interviewed thirteen people, including the plaintiff, his attorneys, the plaintiff’s supervisor and other UI employees, and where the plaintiff failed to name any witness to corroborate his complaint or to demonstrate that the evidence upon which the commission relied was not trustworthy.11
Finally, we emphasize that the standards of proof applicable to the reasonable cause determination are not the same as those that apply at the hearing stage. Reasonable cause, and the analogous probable cause standard, require a lesser showing than the preponderance of the evidence standard; Ierardi v. Commission on Human Rights & Opportunities, supra; and therefore, the nature of the reasonable cause determination is entirely distinct from a ruling on the merits made after a hearing.
*320The basis for the plaintiff’s discrimination complaint was his contention that, after receiving Dolan’s letter, UI ceased its ongoing efforts to transfer him and thereafter refused even to consider the possibility of a transfer.12 The plaintiff’s complaint and the affidavit filed *321along with his request for reconsideration indicate that he intended to present two different types of proof in support of this claim: (1) direct evidence of discrimination, namely, the statement allegedly made by Manniel that, based on Dolan’s letter, the plaintiff was considered a “medical liability”;13 and (2) evidence of the availability of jobs within UI for which the plaintiff was qualified at the time he was terminated.14
*322The investigator for the commission found that there was “no cause” for crediting the plaintiffs allegations. In addition, he found that UI intended to terminate the plaintiff as a buyer at the end of January on the basis of his poor performance and was not using his hypertension as a pretext for firing him. The commission *323accepted the recommendation of the investigator, thereby adopting his findings, and dismissed the complaint. Finally, the commission accepted the recommendation of its staff attorney to deny the plaintiffs request for reconsideration. The staff attorney’s memorandum clearly indicates that the commission also resolved all issues of material fact in UFs favor.15 The issue, therefore, is whether the investigator’s determination that there was no reasonable cause to believe that UI had commited a discriminatory practice, with which the commission agreed, is reasonable in light of the substantial evidence in the record.
The evidence concerning the statement allegedly made by Manniel that UI considered the plaintiff a “medical liability” necessitated a credibility determination between Manniel and the plaintiff, and the investigator and the commission found that Manniel was the more credible party. As we noted above, it is necessary that the commission be allowed to make such credibility determinations if the reasonable cause determination is to serve its intended purpose of screening claims.16
Before reviewing the evidence concerning UI’s attempts to transfer the plaintiff, we must consider the plaintiff’s performance record because it is relevant to UI’s *324claim that his record was an obstacle to a transfer. This evidence is also relevant because it discounts the inference suggested by the plaintiff that the proximity in time between the receipt of Dolan’s letter and the plaintiff’s termination should necessarily be construed as evidence of discriminatory intent on the part of UI. In addition to the evidence of the plaintiff’s poor performance noted above, the record indicates that the plaintiff had considerable difficulty operating UI’s automated purchasing system. Despite the fact that he had received extra training on the use of this system, the plaintiff showed little improvement and the plaintiff’s supervisor stated that assistant buyers and a new buyer knew more about operating the system than the plaintiff did. In 1986, the plaintiff’s workload was temporarily reduced by approximately one third, yet his problems continued. During October and November, 1987, the plaintiff’s error rate in the processing of requisitions was more than twice that of the buyer with the next highest error rate and more than three times the average rate of errors for the other buyers, despite the fact that the plaintiff processed the fewest number of requisitions. The performance evaluations also reveal that the plaintiff required more than the normal amount of supervision.17
The plaintiff’s employment history supports UI’s contention that his poor record was a major roadblock to its attempts to find another position for him. From 1985 through the time of the plaintiff’s termination, there was an ongoing attempt to accommodate the plaintiff’s requests to transfer to another job. In addition to the performance problems noted above, UI officials also cited attitude problems as reasons why the plaintiff was difficult to transfer. The existence of problems with the *325plaintiff’s attitude toward his work was corroborated by the periodic evaluation reports. Finally, with respect to UI’s conduct after it learned that the plaintiff suffered from hypertension, four UI officials, namely, the plaintiff’s supervisor, the employment manager, the director of purchasing and the manager of training and development, indicated that one last unsuccessful attempt was made to find a position within UI after Dolan’s letter was received.
We do not find it necessary to review in detail the evidence concerning the specific positions that the plaintiff claims were available at the time of his termination. Suffice it to say that the record provides substantial evidence to support the commission’s determination that either the plaintiff was not qualified for the positions or that the positions were not in fact available at that time. Finally, we note that the record also includes evidence that between 1985 and 1989, UI accommodated numerous employees with disabilities that included back problems, hand disabilities, anxiety and stress. We conclude that the commission’s determination that there was no reasonable cause to believe that UI committed a discriminatory practice was reasonable in light of the substantial evidence in the record.
II
The plaintiff next claims that the trial court improperly denied his motion to supplement the agency record by introducing evidence of alleged procedural irregularities that undermined the commission’s determination of no reasonable cause. We conclude that the trial court’s denial of this motion was improper.
General Statutes (Rev. to 1987) § 4-183 (f) provides that an administrative appeal “shall be confined to the record” but that “[i]n cases of alleged irregularities in procedure before the agency, not shown in the record, proof thereon may be taken in the court.” “An appeal *326from an administrative tribunal should ordinarily be determined upon the record of that tribunal, and only when that record fails to present the hearing in a manner sufficient for the determination of the merits of the appeal, or when some extraordinary reason requires it, should the court hear the evidence.” Tarasovic v. Zoning Commission, 147 Conn. 65, 69, 157 A.2d 103 (1959); Levinson v. Board of Chiropractic Examiners, 211 Conn. 508, 530, 560 A.2d 403 (1989). The determination of whether the trial court improperly denied the plaintiff’s motion to supplement the record is made on the basis of the abuse of discretion standard. Leib v Board of Examiners for Nursing, 177 Conn. 78, 93, 411 A.2d 42 (1979); Ierardi v. Commission on Human Rights & Opportunities, supra, 585.
In his complaint, the plaintiff alleged that the commission failed to perform its statutory duty to determine whether reasonable cause existed. The plaintiff also claimed that the commission’s procedures favored the dismissal of cases without regard to merit and prevented the staff of the commission from making fair reasonable cause determinations. The complaint stated that these allegations of procedural irregularities would require the presentation of proof not contained in the agency record.
At the first trial court hearing, the plaintiff sought to introduce the testimony of James Noonan, the commission’s investigator on this case; Philip Murphy, commission counsel; and Leslie Brett, chairperson of the commission. The plaintiff contended that the testimony of these three witnesses would establish that: (1) neither Noonan nor the commission applied the “reasonable cause” standard in deciding whether to dismiss the plaintiff’s complaint; and (2) the commission had a quota system whose goal was to close a certain number of cases each month, and, as a result of this system, Noonan was pressured to reach a “no cause” *327finding in this case.18 The trial court denied the motion to supplement the record on the grounds that: (1) the record was sufficient for the issues that the court had to address; and (2) the plaintiffs motion to supplement the agency record was untimely and failed to give the defendant proper notice.
The plaintiff aptly notes that, assuming his allegations of procedural irregularities are correct, the first rationale proffered by the trial court for its decision would be appropriate only if the court conducted a de novo review of the evidence underlying the commission’s determination of no reasonable cause. When, however, the trial court applies the substantial evidence test in reviewing the commission’s decision to dismiss the complaint, as it did in this case, it is inappropriate to refuse extrinsic evidence of alleged procedural irregularities on the ground that the existing record is adequate to conduct the review. The substantial evidence test assumes that an agency’s decision is not tainted by procedural irregularities that implicate the validity of the decision itself. Where there is a question, as there is in this case, as to whether an agency favored a certain outcome or applied an incorrect standard in reaching its decision, the court must determine whether the alleged procedural irregularities did in fact occur before it can utilize the substantial evidence test.
*328With respect to the second rationale offered by the trial court for its refusal to allow the agency record to be supplemented, we first note that the plaintiff’s complaint initiating his appeal clearly stated he sought to supplement the record in order to prove his allegations of procedural irregularities.19 Moreover, neither the Practice Book nor the General Statutes requires a party to file a written motion to supplement the agency record. Consequently, because of the potentially crucial impact of the plaintiff’s claims of procedural irregularities on the propriety of the commission’s decision, we conclude that the trial court abused its discretion in denying the plaintiff the opportunity to present evidence to supplement the agency record.20
*329It is necessary, therefore, that the trial court provide the plaintiff with that opportunity and then determine whether the commission’s decision was tainted by procedural irregularities. If the trial court agrees either with the plaintiff’s contention that an improper standard was used or with his assertion that Noonan was pressured to reach a finding of no reasonable cause, then the trial court must remand the case to the commission for a new determination of reasonable cause using the proper standard.21 If, however, the trial court determines that the plaintiff’s claims of procedural irregularities are not supported by the evidence presented, then no further proceedings are necessary.
The case is remanded for further proceedings in accordance with this opinion.
In this opinion Peters, C. J., Covello and F. X. Hennessy, Js., concurred.