Question

Suppose that 24.5% of all vehicles on the road get a fuel economy of at least 35 miles per gallon (MPG). You conduct an observational study on a stretch of road outside of campus and record the make and model of 824 vehicles over a month long period. What is the probability that greater than 22.23% of the cars you observed get at least 35 MPG? 1. 0.9351 2. -7.4502 3. 0.0649 4. >0.999 5. 0.5000

Answer 1

Population proportion), p = 0.245

Sample size, n = 824

For sample proportion ,

P( < A) = P(Z < (A - )/)

= p = 0.245

=

=

= 0.015

P(greater than 22.23% of the cars you observed get at least 35 MPG) = P( > 0.2223)

= 1 - P( < 0.2223)

= 1 - P(Z < (0.2223 - 0.245)/0.01498)

= 1 - P(Z < -1.515)

= 1 - 0.0649

= 0.9351