Question

In: Statistics and Probability

A city has located in a specific geographic area. It has several snowy days. On 76...

A city has located in a specific geographic area. It has several snowy days. On 76 of 350 randomly selected days, it snows. Find a 99% confidence interval for the true proportion of days on which it snows.

Solutions

Expert Solution

Solution :

Given that,

n = 350

x = 76

Point estimate = sample proportion = = x / n = 76/350=0.217

1 -   = 1-0.217 =0.783

At 99% confidence level the z is ,

  = 1 - 99% = 1 - 0.99 = 0.01

/ 2 = 0.01 / 2 = 0.005

Z/2 = Z0.005 = 2.576 ( Using z table )

  Margin of error = E = Z/2   * (((( * (1 - )) / n)

= 2.576* (((0.217*0.783) / 350)

= 0.057

99% confidence interval for the true proportion,is

- E < p < + E

0.217 - 0.057 < p < 0.217 + 0.057

0.160< p < 0.274

(0.16 ,0.274)

The 99% confidence interval for the population proportion p is :


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