Practice Quiz 9
Statistics 200
Fall 2007
Dr. Nancy Pfenning
1. (5 pts.) Domestic goats follow gaze direction and use social cues in an object choice
task, published online in Animal Behavior in January of 2005, included information on
goats’ performance in a bucket-selection task. Based on the data obtained, we want
to determine if a sample of 13 adult goats tended to be more successful in picking the
bucket with food when cued by the experimenter pointing at it with a finger, compared
to control conditions where no cue was given.
Point 13 10.923 2.691 0.746
Control 13 9.308 1.437 0.398
Difference 13 1.615 3.477 0.964
T-Test of mean difference = 0 (vs > 0): T-value = XXXXX P-Value = 0.060
(a) The data arise from a (i) two-sample (ii) paired design.
(b) The t-statistic has been X-ed out. Based on the size of the p-value, the t-statistic
must be (i) large (ii) not large (iii) borderline
(c) Are you convinced that in general goats respond to the pointing cue?
(Answer yes or no or inconclusive.)
(d) Based on your conclusion in (c), would a confidence interval for population mean
of differences contain zero?
(Answer yes or no or borderline.)
(e) What would the p-value have been if a two-sided alternative had been used?
(f) Would the sample difference have been more convincing if the sample size were
much larger?
