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21) A researcher wants to know whether there is a difference in the physical activity level of children during the morni...

21) A researcher wants to know whether there is a difference in the physical activity level of children during the morning and afternoon. He observes a total of 40 children (20 boys and 20 girls) from randomly selected schools during morning and afternoon recess and gives each child a score (out of 50) based on how much of the time they spend sitting, standing, walking or running. Each child receives a score in the morning and another in the afternoon. If he wants to test whether there is a difference between the individual children's activity level scores in the morning versus the afternoon, what is the appropriate test and should it be a one or two tailed test?

a) z test, one tail b) one-sample t test, two-tail c) paired sample t test, two tail D) Paired sample t test, one tail

22) Population A has a larger standard deviation than Population B. If samples of equal size are taken from both populations, which sample will have a smaller standard error of the mean?

a) Unable to determine with provided information b) the sample from Population c) the sample from Population d) The samples will have the same standard error of the mean

23) A researcher has done a study to look at wether senior citizens sleep fewer hours than the general population. She has gathered data on 30 senior citizens regarding how many hours of sleep they get each night. She performs a two-tailed single-sample t test with a .05 alpha level on her results. She calculates her obtained statistic (tobt) = -1.98. Tcrit for a two tailed t test with an alpha level of .05 and with df=29 is +/-2.045. What decision should she make?

a) Retain the null. absolute value of tobt > absolute value of tcrit b) Reject the null. absolute value of tobt > absolute value of tcrit c) Retain the null. absolute value of tobt < absolute value of tcrit d) Reject the null. absolute value of tobt < absolute value of tcrit

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Ans:

21)

As,same subject is measured at different times,so we will use paired t test.It will be two tailed test,as we want to know if there is difference in score.

Option c is correct.

paired sample t test, two tail

22)

standard error of mean=s/sqrt(n)

As,sample sizes are same,so population with smaller standard deviation will have smaller standard error of mean.

Correct option is:

the sample from Population B

23)

tobt=-1.98

critical t value=+/-2.045

rejection region: t<-2.045 or t>2.045

Option c is correct.

Retain the null. absolute value of tobt < absolute value of tcrit

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