<PAGE>

                                                                    Exhibit 10.2

                               THIRD AMENDMENT TO
                              INVESTMENT AGREEMENT

         THIS THIRD AMENDMENT TO INVESTMENT AGREEMENT (this "Third Amendment")
is made as of September 29, 2002 by and between OPINION RESEARCH CORPORATION, a
Delaware corporation (the "Company") and ALLIED CAPITAL CORPORATION and ALLIED
INVESTMENT CORPORATION, each a Maryland corporation (collectively referred to
herein as "Allied Capital").

                                    RECITALS:

         A. Allied Capital invested the aggregate sum of Fifteen Million Dollars
($15,000,000) in the Company, in exchange for certain subordinated debentures of
the Company and Warrants to purchase shares of Common Stock of the Company
pursuant to that certain Investment Agreement dated as of May 26, 1999 by and
between the Company and Allied Capital (as amended, the "Investment Agreement").

         B. The parties desire to modify certain provisions of the Investment
Agreement.

            NOW, THEREFORE, in consideration of the foregoing Recitals and the
mutual covenants contained herein, and other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, Allied Capital and
its successors and assigns with respect to any of the Debentures or any of the
Warrants (as those terms are hereinafter defined) (individually, a "Holder" and
collectively, the "Holders") and the Company hereby agree as follows:

            1. Definitions. All capitalized terms used herein without definition
shall have the meanings given to such terms in the Investment Agreement.

            2. Amendments to Investment Agreement. The following amendments to
the Investment Agreement shall take effect as of the date hereof:

               (a) Notwithstanding the provisions of Section 5.13(a) of the
Investment Agreement, the Company shall maintain the following maximum ratio of
Indebtedness as of the last day of such calendar quarter ending on the date set
forth below to Adjusted EBITDA for the 12 month period ending on such day:

                           Period                              Ratio
                           ------                              -----
             September 30, 2002                                4.25 : 1
             December 31, 2002                                 4.00 : 1
             March 31, 2003                                    4.00 : 1
             June 30, 2003 and thereafter                      3.75 : 1

               (b) Notwithstanding the provisions of Section 5.13(b) of the
Investment Agreement, the Company shall maintain the following minimum ratios of
EBITDA for the 12

<PAGE>

month period ending on the last day of such calendar quarter ending on the date
set forth below to Principal and Interest for the 12 month period ending on the
last day of such calendar quarter:

                               Period                        Ratio
                               ------                        -----
                 September 30, 2002                          1.05 : 1
                 December 31, 2002                           1.25 : 1
                 March 31, 2003                              1.35 : 1
                 June 30, 2003 and thereafter                1.60 : 1

               3. Closing Conditions. The obligations of Allied Capital to enter
into this Third Amendment and to perform its obligations hereunder are subject
to the satisfaction of the following conditions on or prior to the date hereof:

                  (a) The representations and warranties set forth herein shall
be true and correct on and as of the date hereof.

                  (b) The Company shall be in compliance with all the terms and
provisions set forth herein and in each other Investment Document on its part to
be observed or performed, and at the time of and immediately after the date
hereof, no Event of Default or Default or event or condition that, after the
giving of notice, passage of time, failure to cure or all of the foregoing would
constitute an Event of Default, shall have occurred and be continuing.

                  (c) Allied Capital shall have received the following items:

                      (i)   this Third Amendment, duly executed by the Company;

                      (ii)  a duly executed copy of the Eighth Amendment to the
Credit Agreement by and between the Company and the Senior Lender modifying the
financial covenants in the Senior Credit Facility and otherwise in form and
substance satisfactory to Allied Capital;

                      (iii) all amounts due and payable under the Investment
Documents on or prior to the date hereof, including without limitation
reimbursement or payment of all out-of-pocket expenses and the amendment fee
required to be reimbursed or paid by the Company hereunder; and

                      (iv)  such other documents, instruments and information as
Allied Capital may reasonably request.

               4. Representations and Warranties. To induce Allied Capital to
execute and deliver this Third Amendment, the Company hereby reaffirms all
covenants, representations, and warranties made in the Investment Agreement and
the other Investment Documents to the extent the same are not amended hereby and
agree that all such covenants, representations, and warranties shall be deemed
to have been remade as of the date of this Third Amendment, except to the extent
that they expressly relate by their terms to a prior date. Any default by the
Company in its

                                      -2-

<PAGE>

warranties and representations made in this Third Amendment shall constitute an
additional Event of Default under the Investment Agreement, as amended hereby.

               5. Acknowledgments by Company. The Company acknowledges and
agrees with the Holders that as of the date hereof, the aggregate principal
amount of the Obligations owing by the Company to Allied Capital under the
Investment Agreement is $15,000,000, and all such Obligations are due and owing
by Company to Allied Capital without any defense, deduction, offset, or
counterclaim of any nature (all of which are hereby waived).

               6. Reference to and Effect Upon Investment Agreement. Each
reference in the Investment Agreement to "this Agreement," "hereunder,"
"hereof," or words of like import shall hereafter mean and be a reference to the
Investment Agreement, as amended hereby and from time to time. Except as
specifically amended hereby, the Investment Agreement, the other Investment
Documents, and each and every term and provision thereof shall remain in full
force and effect and are hereby ratified and confirmed. The execution, delivery,
and effectiveness of this Third Amendment shall not operate as a waiver of any
right, power, or remedy of the Holders under the Investment Agreement or the
other Investment Documents or constitute a waiver of any provision of the
Investment Agreement or the other Investment Documents.

               7. Fees and Expenses. The Company shall pay all fees and expenses
incurred by Allied Capital in connection with the preparation, negotiation,
execution, and delivery of this Third Amendment and any related documents,
including, without limitation, the fees and expenses of its counsel and
out-of-pocket expenses, including reasonable due diligence expenses, on or prior
to the date hereof. The Company shall also pay to Allied Capital a
non-refundable amendment fee in the amount of $18,750.

               8. Release. The Company acknowledges that Allied Capital has
fulfilled all of its obligations under the Investment Agreement and hereby
releases and forever discharges the Holders and their representatives, agents,
employees, attorneys, successors, directors, officers, parents, affiliates,
assigns, and subsidiaries (collectively the "Releasees") of, to, and from any
and all claims, defenses, actions, causes of action, suits, controversies,
agreements, provisions, and demands in law or in equity, known or unknown
(collectively, the "Claims") which the Company ever had, now has, or may have
arising from or relating to the Investment Documents, against or related to the
Releasees, through the date of this Third Amendment. The Company agrees to
assume the risk of any and all unknown, unanticipated or misunderstood claims
which are released hereby.

                                      -3-

<PAGE>

           9.  Miscellaneous.

               (a) Entire Agreement; Integration Clause. This Third Amendment
and the other Investment Documents set forth the entire agreements and
understandings of the parties hereto with respect to this transaction, and as
such supersede any prior agreements, whether written or oral, regarding the
matters described herein.

               (b) No Oral Modification or Waivers. The terms herein may not be
modified or waived orally, but only by an instrument in writing signed by the
party against which enforcement of the modification or waiver (as the case may
be) is sought.

               (c) Governing Law. This Third Amendment is governed by, and
interpreted and construed in accordance with, the internal laws of the State of
Maryland (without regard to its conflicts of law principles).

               (d) Headings. The headings of the paragraphs and sub-paragraphs
of this Third Amendment are inserted for convenience only and shall not be
deemed to constitute a part of this Third Amendment or the other Investment
Documents.

               (e) Severability. To the extent any provision herein violates any
applicable law, that provision shall be considered void and the balance of this
Third Amendment shall remain unchanged and in full force and effect.

               (f) Counterparts. This Third Amendment may be executed in as many
counterpart copies as may be required. It shall not be necessary that the
signature of, or on behalf of, each party appear on each counterpart, but it
shall be sufficient that the signature of, or on behalf of, each party appear on
one or more of the counterparts. All counterparts shall collectively constitute
a single agreement. It shall not be necessary in any proof of this Third
Amendment to produce or account for more than a number of counterparts
containing the respective signatures of, or on behalf of, all of the parties.

                      [Signatures appear on following page]

                                      -4-

<PAGE>

         IN WITNESS WHEREOF, the undersigned have executed and delivered this
Third Amendment as of the date first above written.

                                  COMPANY:

WITNESS/ATTEST:                   OPINION RESEARCH CORPORATION



 /s/ Stacy Lee                    By: /s/ Kevin P. Croke          (SEAL)
----------------------------          --------------------------
Name: Stacy Lee                   Name:  Kevin P. Croke
                                  Title: EVP & Director of Finance

                                  ALLIED CAPITAL:

WITNESS/ATTEST:                   ALLIED CAPITAL CORPORATION



 /s/ Kenny Eli                    By: /s/ Daniel L. Russell      (SEAL)
---------------------------          ---------------------------
Name:    Kenny Eli                Name:  Daniel L. Russell
                                  Title: Principal

WITNESS/ATTEST:                   ALLIED INVESTMENT CORPORATION



/s/ Kenny Eli                     By: /s/ Daniel L. Russell      (SEAL)
---------------------------           --------------------------
Name:    Kenny Eli                Name:  Daniel L. Russell
                                  Title: Principal

                                      -5-