158.796 Research Methods Assignment 3. Inferential Statistics

Aim: Working individually, demonstrate the ability to calculate and interpret basic inferential statistics.

1.   A researcher believes that transparency increases participation in socio-technical web site. She sets up matched web sites with and without transparency, and gets subjects to try out both, controlling for the order of which one they try out first. After each web site trial, subjects answer questions on how likely they are to contribute to the web site and join its community, where higher numbers indicate higher likelihood. In addition, scores on the inventory are normally distributed. The scores appear below.

Not Transparent               Transparent

46                                      44

41                                      40

42                                      39

47                                      46

43                                      42

45                                      43

a)      What statistical test should be used to analyze these data?

b)      Identify the hypotheses for this study (H0 and Ha).

c)      Conduct the appropriate analysis and give the result.

d)      Should the null hypothesis H0 be rejected? What should the researcher conclude?

e)      If significant, compute the effect size and interpret this.

f)      If significant, draw a graph representing the data.

2. A researcher studies the effect of number of clicks/scroll-downs required to find viewable data to the number of negative words used in blog feedback and gets the following data:

 Clicks/Scroll-downs One Two Three Four 3 4 10 10 5 7 11 13 6 8 13 10 4 3 9 9 2 2 10 10

a)      Show the ANOVA summary table.

a)      Is the result significant at .05?

b)     Perform post-hoc comparisons as necessary

c)      What conclusion can be drawn from the F-ratio and post-hoc comparisons?

d)     Graph the means

e)     What is the effect size and what does it mean?

3.   a) Explain when it would be appropriate to use a t test versus a one-way analysis of variance.

b) If in an ANOVA the null hypothesis is true, what value should we expect for the F-ratio? Explain your answer clearly.

Deliverables: Submit printed copy of report at the beginning of class on the due date

Stated requirements (-5 each if not met). Cover sheet must have this statement of academic integrity, which is signed:

I declare that this assignment is entirely my own work and that it has not been taken from the work of others. When the work and ideas of others have been used in the study, that work has been properly cited in the text. This assignment does not contain any unacknowledged work from any other source.

Signature:       ________________________________

It must be written in academic style, e.g. don't use personal pronouns. Must be spell and grammar checked. Must be printed and stapled.