The information given below is used in Questions 22–25. Please show work! At wha
ID: 3156035 • Letter: T
Question
The information given below is used in Questions 22–25.
Please show work!
At what age do babies learn to crawl? Does it depend on the time of the year that babies are born? Data were collected from parents who brought their babies into the University of Denver’s Infant Study Center to participate in one of a number of experiments between 1988 and 1991. Parents reported the birth month and the age in which their child was first able to creep or crawl a distance of four feet within one minute. The resulting data were grouped by month of birth: January, May, and September.
Birth month
Mean
Std. dev.
n
January
29.84
7.08
32
May
28.58
8.07
27
September
33.83
6.93
38
Crawling age is given in weeks. Assume that the data can be considered as three independent random samples, one from each of the populations comprised of babies born in that particular month, and that the populations of crawling ages have Normal distributions.
An ANOVA was run on the data. The following shows a portion of the results.
Source
df
Sums of squares
Mean square
F-ratio
Group
505.26
Error
53.45
Total
22. The alternative hypothesis for the ANOVA is that the mean age at which babies learn to crawl is
a. highest in September.
b. different for the three birth months.
c. the same for January and May.
d. the same for all months in the year.
23. The mean square for groups is
a. 5.38.
b. 252.63.
c. 1010.52.
d. 1515.78.
24. The pooled standard deviation is
a. 7.31.
b. 17.63.
c. 22.48.
d. 26.73.
25. The value of the F statistic is
a. 3.15.
b. 4.73.
c. 6.30.
d. 9.45
Birth month
Mean
Std. dev.
n
January
29.84
7.08
32
May
28.58
8.07
27
September
33.83
6.93
38
Explanation / Answer
ANOVA TABLE
25) F cal=4.727
24) Pooled standard deviation= sqrt(MSE) =sqrt(53.45) =7.31
23)The mean square for groups is 252.67
22) that the mean age at which babies learn to crawl is different for three birth months
SS df MS F p Between: 505.254 2 252.627 4.727 0.011 Within: 5,024.09 94 53.448 Total: 5,529.34 96Related Questions
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