Question

A software engineer is creating a new computer software program. She wants to make sure that the crash rate is extremely low so that users would give high satisfaction ratings. In a sample of 780 users, 39 of them had their computers crash during the 1-week trial period.

(a)

What is the sample size?

What is p̂?

(b)

What is the 95% confidence interval for p̂? (Use a table or technology. Round your answers to three decimal places.)

Answer 1

The software engineer sampled 780 users.

a) So, the sample size = 780

The proportion of users who had their computer crash , denoted by , is :

   = ( 39/780 )

= 0.05

b) The 95% confidence interval for   is given by   (   [z * {(1 -   ) / n}] )

From the z table, we know, z for 95% CI = 1.96

So, the interval is = (   [z * {(1 -   ) / n}] )

= 0.05 0.015

= ( 0.035 , 0.065 )