Assignment:
Does cocaine use by pregnant women cause their babies to have low birth weight?
To study this question, birth weights of babies of women who tested positive for cocaine/crack during a drug-screening test were compared with the birth weights for babies whose mothers either tested negative or were not tested, a group we call "other"
Here are the summary statistics. The birth weight s are measured in grams.
Group n Sample mean Standard deviation s
Positive test 134 2733 599
Other 5974 3118 672
Formulate appropriate null and alternative hypotheses.
(M1 - the mean birth weight of babies of woman who tested positive,
M2 - the mean birth weight of babies of woman who either tested negative or were not tested)
a. Ho: M1 is not equal to M2.
Ha: M1 is equal to M2.
b. Ho: M1 is equal to M2.
Ha: M1 is not equal to M2.
c. Ho: M1 is greater than M2.
Ha: M1 is equal to M2.
d. Ho: M1 is equal to M2.
Ha: M1 is less than M2.
e. Ho: M1 is less than M2.
Ha: M1 is equal to M2.
Answer:
(d) Ho: M1 is equal to M2.
Ha: M1 is less than M2.
Q1: Find the value of the test statistic. Assume that the standard deviation for both populations is the same and use the pooled variance.
a. -6.57
b. -3.42
c. -1.45
d. 1.45
e. 3.42
f. 6.57
Q2: Find the P-value of the test.
a. -0.123
b. 0
c. 0.123
d. 0.367
e. 0.582
f. 1.34
Q3: For the problem give a left endpoint (lover limit, lower boundary) of the 95% confidence interval fo the mean difference (M1 - M2) in birth weights.
(M1 - the mean birth weight of babies of woman who tested positive,
M2 - the mean birth weight of babies of woman who either tested negative or were not tested)
a. - 543.15
b. -488.79
c. -385.67
d. -281.21
e. -126.41
f. 126.41
g. 281.21
h. 385.67
Q4: Give a right endpoint (upper limit, upper boundary) of the 95% confidence interval for the mean difference (M1 - M2) in birth weights.
(M1 - the mean birth weight of babies of woman who tested positive,
M2 - the mean birth weight of babies of woman who either tested negative or were not tested)
a. - 543.15
b. -488.79
c. -385.67
d. -281.21
e. -126.41
f. 126.41
g. 281.21
h. 385.67