At what age do babies learn to crawl Does it depend on the t

At what age do babies learn to crawl? Does it depend on the time of the year that babies were 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 at 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.

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 F test 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

Use this information to match the below.

The numerator degrees of freedom for the ANOVA F test are

The denominator degrees of freedom for the ANOVA F test are

The alternative hypothesis for the ANOVA F test is

The mean square for groups is

The pooled standard deviation is

The value of the ANOVA F-statistic is

7.31.

53.45.

2.

96.

3.15.

the mean age at which babies learn to crawl is the same for January and May.

94.

22.48.

the mean age at which babies learn to crawl is highest in September.

17.63.

252.63.

1515.78.

4.73.

1010.52.

3.

not all the mean ages, at which babies learn to crawl during these months, are the same.

Birth Month	Mean	Standard deviation	n
January	29.84	7.08	32
May	28.58	8.07	27
September	33.83	6.93	38

Solution

At what age do babies learn to crawl? Does it depend on the time of the year that babies were 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 at 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

Standard deviation

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.

source

DF

SS

MS

F

Group

2

505.26

252.63

4.73

Error

94

5024.3

53.45

Total

96

5529.56

Use this information to match the below.

Answer

-A.B.C.D.E.F.G.H.I.J.K.L.M.N.O.P.

The numerator degrees of freedom for the ANOVA F test are

C   2

-A.B.C.D.E.F.G.H.I.J.K.L.M.N.O.P.

The denominator degrees of freedom for the ANOVA F test are

G 94

-A.B.C.D.E.F.G.H.I.J.K.L.M.N.O.P.

The alternative hypothesis for the ANOVA F test is

P not all the mean ages, at which babies learn to crawl during these months, are the same.

-A.B.C.D.E.F.G.H.I.J.K.L.M.N.O.P.

The mean square for groups is

K    252.63

-A.B.C.D.E.F.G.H.I.J.K.L.M.N.O.P.

The pooled standard deviation is

A     7.31

-A.B.C.D.E.F.G.H.I.J.K.L.M.N.O.P.

The value of the ANOVA F-statistic is

M 4.73

Birth Month	Mean	Standard deviation	n
January	29.84	7.08	32
May	28.58	8.07	27
September	33.83	6.93	38