Political Contributions: Listed below are contributions (in dollars) made to the two presidential candidates in a recent election. All contributions are from the same zip code as the author, and the data are from the Huffington Post. Do the contributions appear to favor either candidate? What do you conclude after learning that there were 66 contributions to Obama and 20 contributions to McCain.

Question

McCain:
50
75
240
305
250
700
350
500
1250
1500
500
500
40
221
400

Obama:
275
452
300
1000
1000
500
100
1061
1200
235
875
2000
350
210
250

Answer 1

Z = (mean1 - mean2)/standard error (SE) of difference between means

SEdiff = √(SEmean1^2 + SEmean2^2)

SEm = SD/√n

If only one SD is provided, you can use just that to determine SEdiff.

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score. Does it exceed your level of significance?

Going only with the number of contributions favors Obama.