At What Age Do Babies Learn to Crawl? Does It

question 1

Multiple Choice

At what age do babies learn to crawl? Does it take longer to learn in the winter when babies are often bundled in clothes that restrict their movement? Data were collected from parents who brought their babies into the University of Denver 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 4 feet within 1 minute.The resulting data were grouped by month of birth: January,May,and September: Crawling age is given in weeks.Assume the data represent three independent simple random samples,one from each of the three populations consisting of babies born in that particular month,and that the populations of crawling ages have Normal distributions. A partial ANOVA table is given below. The null hypothesis for the ANOVA F test is that the population mean crawling ages are equal for all three birth months.What is the alternative hypothesis?

• A)The population mean crawling age is larger for January than the other 2 months.
• B)The population mean crawling age is larger for May than the other 2 months.
• C)The three population mean crawling ages are all different from each other.
• D)Not all three population mean crawling ages are equal to each other.

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