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a relief fund is set up to collect donations. a random sample of 400 people shows that 28% of those 200 who were contacted by telephone actually made contributions compared to only 18% of the 200 who received mail requests. is there a difference between the proportions of people who make donations when contacted by telephone or mail? use the 0.05 level of significance

Sagot :

At the 0.05 significance level,

the lower limit of confidence interval is approx. 0.018 and upper limit of confidence interval is approx.0.182...

A relief fund is set up to collect donations.

first Sample size, n₁ = 200

Second sample, n₂ = 200

28% of those 200 people's who contacted by telephone , p₁-cap = 28% = 0.28

18% of the 200 who received mail requests, p₂-cap = 0.18

significance level, α = 0.05

S.E for difference between proportions

= √(p₁-cap(1-(p₁-cap))/n₁ + p₂-cap(1-(p₂-cap))/n₂)

= √0.28(1-0.28)/200 + 0.18(1-0.18)/200

= √0.28(0.72)/200 + 0.18(0.82)/200

= 0.04178 ~ 0.0418

the z-value for significance level 0.05, Zα/2 = Z₀.₀₂₅ = 1.96 (from Z-table)

Margin of error = α/2 ( S.Eₚ₁ ₋ₚ₂)

= 1.96× 0.0418 = 0.08189

CI is given by (p₁-cap - p₂-cap) +- Zα/2 ( S.E )

Lower limit = (0.28-0.18)+ 0.08189

=0.01818 ~ 0.018

Upper limit = (0.28-0.18) - 0.08189

= 0.18189~0.182

To learn more about Confidence interval, refer:

https://brainly.com/question/17212516

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