Name_____________________________________________ Hypothesis Testing with the Independent Samples t-test 1.
The owner of the Shine Company, which manufactures cleaning supplies, suspected that adding a fragrance to a window cleaner leads people to believe that it cleans better than an unscented product. The company selected 24 participants and randomly assigned 12 of them to the scented cleaner and 12 to the unscented cleaner. They had each person use it to clean a set of windows and then complete a survey on how well the cleaner worked. The survey yielded a numerical value, the “cleaning index,” with higher numbers indicating better cleaning.
a.
What are the nondirectional hypotheses? H
O
: μ
scented
μ
unscented or μ
scented
–
μ
unscented
0 H
1
: μ
scented
μ
unscented or μ
scented
–
μ
unscented
0 b.
What is the df for this example? c.
You collect your data, analyze with jamovi, and find that: •
Scented group: M
= 7.5, SD
= 1.57 •
Unscented group: M
= 6.0, SD
= 1.13 •
t
= 2.69 •
p
= 0.013 •
d = 1.10 d.
Do you reject the null hypothesis (assume the standard alpha level of .05)? (Check one)
YES
NO e.
Based on these data, which of the following is true? (Check one) A. Windows cleaned with the scented product were rated as cleaner than the windows cleaned with the unscented product. B. Windows cleaned with the unscented product were rated as cleaner than the windows cleaned with the scented product. C. There was no significant difference in the “cleaning index” between windows cleaned with the scented product and windows cleaned with the unscented product. f.
How would you characterize the effect size? g.
State your results as if you were writing them for a journal. t
( )= , p
, d = . h.
What are the directional hypotheses? H
O
: μ
scented
μ
unscented H
1
: μ
scented
μ
unscented Adapted from: Steinberg, W.J. (2008). Statistics Alive!
Thousand Oaks, CA: Sage.
