Question

Last year, I conducted a survey and found that 83% of CSU students said Statistics was their favorite class. If I wanted to do this study again, how many students should I survey so that I can have 90% confidence and a margin of error of 5%.

Answer 1

Solution :

Given that,

= 0.83

1 - = 1 - 0.83= 0.17

margin of error = E = 5% = 0.05

At 90% confidence level

= 1 - 90%  

= 1 - 0.90 =0.10

/2 = 0.05

Z/2 = Z0.05 = 1.645 ( Using z table )

Sample size = n = (Z/2 / E)2 * * (1 - )

= (1.645 / 0.05)2 * 0.83 * 0.17

=152.73

Sample size = 153