91Ó°ÊÓ

Given in the question that,

$99\%$CI from $-20to15$ we have to calculate the interpretation of confidence level.

The mean found in a sample is thought to represent the best estimate of the population's true value. The sample mean of $99\%$percent Cl is interpreted as a range of values containing the genuine population mean with probability $0.99or99\%$.

Finding a confidence interval for the difference between two means can be used to compare two population means.

Assume that ${\mathrm{μ}}_1$is the mean of a variable in population $1$and ${\mathrm{μ}}_2$is the mean of a variable in population $2$. The sampling distribution of the difference between two means is then ${\mathrm{μ}}_1-{\mathrm{μ}}_2$.

Given a$99$percent confidence interval, Cl ranges from$-20to15$

The confidence interval's endpoints are both positive values in this case.

This means that ${\mathrm{μ}}_1-{\mathrm{μ}}_2$is $99\%$ certain to exist someplace.