Question

# Suppose that you sample 28 high school baseball pitchers in one country and find that they...

Suppose that you sample 28 high school baseball pitchers in one country and find that they have a mean fastball pitching speed of 80.5mph with a standard deviation of 5.2 mph.

a. find a point estimate for the mean fastball pitching speed of all high school baseball pitchers in the country.

b. find a 99% confidence interval for the mean fastball pitching speed of all high school baseball pitchers in the country.

n=

x bar=

s or sigma value=

z or t value=

df (of none, type NA=

error=

LCL=

UCL=

Here, the sample size , n = 28

the sample mean , = 80.5

sample standard deviation , s = 5.2

a) a point estimate for the mean fastball pitching speed of all high school baseball pitchers in the country is the sample mean.

Therefore , point estimate = 80.5

b)We have to find a 99% confidence interval.

We use the t distribution.

Degrees of freedom = n - 1 = 27

Using the t critical values table, at 99% confidence level and df = 27 , the critical value is , t = 2.77

The confidence interval is =  t*s/ n

= 80.5 2.77 * 0.98

= 80.5 2.723

= (77.78 , 83.22)

LCL = 77.78

UCL = 83.22

error = 2.723