In 22 patients with an unusual liver disease, the plasma alkaline phosphatase had a mean value of 39 IU/l (International Units per liter), standard deviation = 3.4 IU/l. Calculate the 95% confidence interval for the population’s true mean value of plasma alkaline phosphatase.
My equation
Step 1. Determine t*-value w/ t-table list.
T=22-1=21; t*=2.080
Step 2.Solve for x, s, and n
X=39IU/1, S=3.4 IU/1 n=22
Step 3. Margin of error
2.080(3.4IU/Sqrt(22))=+-1.51
Confidence Interval: 39+- 1.51; Range for true population mean:37.49 to 40.51
I'm curious if this is the correct formula.
My equation
Step 1. Determine t*-value w/ t-table list.
T=22-1=21; t*=2.080
Step 2.Solve for x, s, and n
X=39IU/1, S=3.4 IU/1 n=22
Step 3. Margin of error
2.080(3.4IU/Sqrt(22))=+-1.51
Confidence Interval: 39+- 1.51; Range for true population mean:37.49 to 40.51
I'm curious if this is the correct formula.