The following data represent the age (in weeks) at which babies first crawl base

Question

The following data represent the age (in weeks) at which babies first crawl based on a survey of 12 mothers. Because the sample size small, we must verify that the data come from a population that is normally distributed and that the sample size does not contain any outliers Are the conditions for constructing a confidence interval about tie mean satisfied? Construct a 95% confidence interval for the mean age at which a baby first crawls. Select the correct choice below and fill in any answer boxes in your choice What could be done to increase the accuracy of the interval without changing the level of confidence?

Explanation / Answer

a.
yes population is normalley distributed and sample does not have a outlier
b.
Confidence Interval
CI = x ± t a/2 * (sd/ Sqrt(n))
Where,
x = Mean
sd = Standard Deviation
a = 1 - (Confidence Level/100)
ta/2 = t-table value
CI = Confidence Interval
Mean(x)=40.5
Standard deviation( sd )=8.63
Sample Size(n)=12
Confidence Interval = [ 40.5 ± t a/2 ( 8.63/ Sqrt ( 12) ) ]
= [ 40.5 - 2.201 * (2.491) , 40.5 + 2.201 * (2.491) ]
= [ 35.017,45.983 ]
c.
either increase or decrease a sample size

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