Number 7 please help
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The confidence interval for the meannumber of dresses purchased each year is (7.2,7.4).
Given sample mean of 7.3 and sample standard deviation of 1.4 and confidence interval of 95%.
We have to find confidence interval for the mean number of dresses purchased each year.
Because the sample size is more than 30 so z test test will be used.
Margin of error is the difference in real values and calculated values.
Margin of error=z*σ/
where zis the criticalvalue of confidence level.
σ is sample standard deviation,
n is sample size.
z value for 95% confidence level=1.96
Margin of error=1.96*1.4/
=2.744/22.869
=0.12
Upper level= Mean + margin of error
=7.3+0.12
=7.42
Rounding off
=7.4
Lower level=Mean - margin of error
=7.3-0.12
=7.18
Rounding
=7.1
Hence the confidence interval is (7.1,7.4).
Learn more about confidence interval at brainly.com/question/15712887
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