Question

The reading speed of second grade students in a large city is approximately​ normal, with a mean of 91 words per minute​ (wpm) and a standard deviation of 10 wpm.

Complete parts​ (a)

What is the probability that a random sample of 26 second grade students from the city results in a mean reading rate of more than 95 words per​ minute? The probability is _________ ​(Round to four decimal places as​ needed.)

Answer 1

Solution :

Given that,

mean = = 91

standard deviation = = 10

n = 26

= 91

₌ / n = 10 26 = 1.9612

P ( 95 )

= 1 - P (    95 )

= 1 - P ( - /)   (95 - 91/1.9612)

= 1 - P( z   4 / 1.9612 )

= 1 - P ( z 2.04 )   

Using z table

= 1 - 0.9793

= 0.0207

Probability = 0.0207