1. Jun 8, 2009

ssupaman786

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 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 F test was run on the data. The following shows a portion of the results.
Source df Sums of squares Mean square
Group
505.26

Error

53.45
Total

The pooled standard deviation is?
i keep having problems with this question...