# Probability and statistics ques

1. Jun 22, 2008

### sstudent

QUES: the yield of a chemical process is bieng studied. the past 5 days of plant operation have resulted in :91.6, 88.75, 90.08, 89.95, 91.3. Find a 95% two-sided confiendce interval. Thanks folks

2. Jun 22, 2008

### rootX

3. Jun 22, 2008

### sstudent

i tried using the eqautaion "Confiendnce interval on the mean, varaiance known" but i am not sure how to get the variance. thanks

4. Jun 23, 2008

### konthelion

Let $$\bar{x}$$ be the sample mean, what is $$\bar{x}$$?
What is n, the sample size?
What is s, the sample standard deviation?
What distribution should you use(based on n)? Then find the 95% confidence interval.