Question

A researcher hypothesizes that a person who drops a stack of books and uses profanity will be less likely to gain help (defined as whether or not someone helps pick up the books) than someone who does not use profanity. He flips a coin to randomly assigns participants to each condition, one group says, “Oh darn” and the other says, “Oh s..t” after dropping several books. The researcher then records whether or not a bystander helped pick up the books. The results are listed below. Assume a two-tailed test with .05 level of significance and equal distribution.

		bystander helped	bystander did not help	TOTAL
no profanity	actual count	23	16	39
	expected count	18.5	20.5	39.0
profanity	actual count	14	25	39
	expected count	18.5	20.5	39.0
TOTAL	actual count	37	41	78
	expected count	37.0	41.0	78.0

a) What is the appropriate chi-square test?

b) State the null and alternative hypothesis.

c) In reading the crosstabulation chart, what is the actual amount of no profanity, bystander helped?

d) What is the expected value?

Answer 1

a) Chi square test of independence is appropriate

$\chi ^2=\sum \frac{(O_f-E_f)^2}{E_f}=4.16$

O is the observed frequency

E is the expected frequency

b) $H_0:$ a person who drops a stack of books and uses profanity will be equally likely to gain help than someone who does not use profanity

$H_a:$a person who drops a stack of books and uses profanity will be less likely to gain help

c) actual amount is 23

d) Expected value is 18.5