Asample of size 36 from a normally distributed population variable with population standard deviation 20 had a sample mean of 88. find a 90% confidence interval for the population mean.

Given the sample mean is and population standard deviation is .

Now the standard deviation of the sample mean is

The confidence interval for population mean is

.

Here

The 90% CI for population mean is

2(2x + 3) = -4 + 2(2x + 5)

4x + 6 = -4 + 4x + 10

4x + 6 = 4x + 6

4x - 6 + 6 = 4x - 6 + 6

4x = 4x

x = x

unlimited solutions.