Question

Suppose that a previous study has indicated that 45% of college students have twitter account. How large of a random sample is needed to be 90% sure that a point estimate will be within a distance of 3% of p?

Answer #1

Solution :

Given that,

= 45%=0.45

1 - = 1 - 0.45 = 0.65

margin of error = E = 3% = 0.03

At 90% confidence level

= 1 - 0.90 = 0.10

/2 =0.05

Z/2 = 1.645 ( Using z table )

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

= (1.645 / 0.03)2 * 0.45 * 0.65

=879.458

Sample size = 879 rounded

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