Question

The state education commission wants to estimate the fraction of tenth grade students that have reading skills at or below the eighth grade level.

Step 2 of 2 : Suppose a sample of 333 tenth graders is drawn. Of the students sampled, 260 read above the eighth grade level. Using the data, construct the 80% confidence interval for the population proportion of tenth graders reading at or below the eighth grade level. Round your answers to three decimal places.

Answer 1

Confidence interval, CI = Z*

Proportion of students that have reading skills at or below the eighth grade level = 1 - 260/333

= 0.2192

For 80% confidence level, Z* = 1.28

= p = 0.2192

=

=

= 0.0227

Confidence interval = 0.2192 1.28x0.0227

= 0.2192 0.0290

= (0.190, 0.248)