# Thread: Interview questions - preventing contamination

1. ## Interview questions - preventing contamination

Hello all,

Recently, I have encountered math problem which I do not know how to solve. I mean, I understand why the suggested answer is correct, but I need to know how to calculate it by myself. I will be very grateful for straight-forward explanation.
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You recently attended a workshop on forensic interviewing techniques. The workshop focused on techniques for preventing interviewer contamination, with the goal of eliciting new details during an interview, while avoiding eliciting details that contradicted prior statements. The following table was presented from a field study to illustrate the effect of question types on the responses during interviews.

The following table was presented from a field study to illustrate the effect of question type on responses during interviews.

Question types and the production of new and contradictory details:

 Question type Number of questions asked Response: new details Response: contradictory details Invitation 56 48 (11%) 0 (0%) Directive 93 71 (17%) 19 (21%) Option-posing 223 158 (38%) 42 (46%) Suggestive 187 144 (34%) 30 (33%)

Note: Numbers in parentheses are percentages within the columns

Questions: Based on the information presented, which question type would you recommend to use during the interviews?

A. Invitation questions
B. Directive
C. Option-posing
D. Suggestive

2. ## Re: Interview questions - preventing contamination

It think that depends largely upon who you choose to value "new detail" versus "contradictory details".

One method would be to treat "contradictory details" as negative new details.

Then the value of the different methods would be:
Invitation 11- 0= 11
Directive 17- 19= -2
Option-posing 38- 46= -8
Suggestive 34- 33= 1
So "Invitation" is best.

Another might be to treat "contradictory details" as reciprocal new details.

Then the value of the different methods would be:
Invitation 11/0= infinity
Directive 17/19= 0.89
Option-posing 38/46= 0.83
Suggestive 34/33= 1.03.

So either method give "Invitation" as being best.

3. ## Re: Interview questions - preventing contamination

Yes, "Invitation" is suggested as correct answer. Thank you very much for your help!