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Testing for Nonresponse Bias. The participation rate
of approximately 15% (i.e., 153/1,050) was somewhat
low and suggested the potential for nonresponse bias. We
therefore conducted a telephone survey of 100 randomly
selected nonparticipants to determine whether there were
any systematic differences between our sample and the
rest of the population. We carried out t-tests for differences
in the means of participating and nonparticipating
firms on certain key variables. No significant differences
in the means were found for the size of firms (t = 1.10),
length of the business relationship with the supplier company
(t = -0.81), or satisfaction with the buyer-supplier
relationship (t = - 0.56). Hence, we believe the threat
to internal validity of the results is limited.

将问卷数据的前部分和后部分数据进行差异性检验