Question

I play Words with Friends often. It is an app which consists of a game like scrabble. I would like to calculate what my average word score is when I play a word. I have kept data from the last 30 words that I played, and my mean is 26.45 points with a standard deviation of 5.48 points. If I want to predict the population mean with 95% confidence, I need to identify what I have. What is my critical value and the confidence interval?

Answer 1

Here, the sample size is n = 30

Sample mean , = 26.45 and sample standard deviation ,s = 5.48

We have to find the 95% confidence interval and we use the t distribution for that purpose.

Degrees of freedom = n - 1 = 29

We look at the t critical values table and find the critical value for t at df = 29 and 95% confidence level.

From the table , t = 2.05 (critical value)

The confidence interval is = t*s/n

= 26.45 2.052

= (24.398 , 28.502)

The interval is (24.4 , 28.5).