In: Statistics and Probability
One of the most impressive, innovative advances in online
fundraising over the past decade is the rise of crowd-funding
websites. While features differ from site to site, crowd-funding
sites are websites that allow you to set up an online fundraising
campaign based around a fundraising page, and accept money
directly from that page using the website's own credit card
processor. A certain crowd-funding website reported that 127 of
347 technology crowd-funding projects were successfully launched
in the past year and 347 of 882 film and video crowd-funding
projects were successfully launched in the past year. Complete
parts (a) through (c) below.
a. Is there evidence of a significant difference in the proportion
of technology crowd-funding projects and film and video
crowd-funding projects that were successful? (Use alpha =
0.1.)
State the null and alternative hypotheses, where pi 1 is the
population proportion of successful technology crowd-funding
projects and pi 2 is the population proportion of successful film
and video crowd-funding projects.
Data:
n1 = 347
n2 = 882
p1 = 127/347 = 0.365994236
p2 = 347/882 = 0.393424036
Hypotheses:
Ho: p1 = p2
Ha: p1 ≠ p2
Decision Rule:
α = 0.1
Lower Critical z- score = -1.644853627
Upper Critical z- score = 1.644853627
Reject Ho if |z| > 1.644853627
Test Statistic:
Average proportion, p = (n1p1 + n2p2)/(n1 + n2) = (347 * 0.365994236311239 + 882 * 0.393424036281179)/(347 + 882) = 0.385679414
q = 1 - p = 1 - 0.385679414157852 = 0.614320586
SE = √[pq * {(1/n1) + (1/n2)}] = √(0.385679414157852 * 0.614320585842148 * ((1/347) + (1/882))) = 0.030845206
z = (p1 - p2)/SE = (0.365994236311239 - 0.393424036281179)/0.030845206015453 = -0.889272711
p- value = 0.373856534
Decision (in terms of the hypotheses):
Since 0.889272711 < 1.644853627 we fail to reject Ho
Conclusion (in terms of the problem):
There is no sufficient evidence of a significant difference in the proportion of technology crowd-funding projects and film and video crowd-funding projects that were successful.
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