A random sample of 81 observations has a mean of 20, a median of 21, a mode of 22, and a standard deviation of 3.6. The 80% confidence interval for the population mean is

The 80% confidence interval for the population mean is  19.48 or 20.52

Step-by-step explanation:

Given that ;

the random sample size n = 81

mean = 20

median  = 21

mode = 22

standard deviation σ = 3.6

The 80% confidence interval for the population mean can be calculated as follows:

Firstly; the degree of freedom df = n - 1

df = 81 - 1

df = 80

At 80% confidence interval the critical value is z =  

The 80% confidence interval for the population mean is  =

= 19.4832 or 20.5168

19.48 or 20.52

yes. we do proportions in probabilities.