question archive From her purchased bags, Rory counted 110 red candies out of 550 total candies
From her purchased bags, Rory counted 110 red candies out of 550 total candies
Subject:StatisticsPrice:2.87 Bought7
From her purchased bags, Rory counted 110 red candies out of 550 total candies. Using a 90% confidence interval for the population proportion, what are the lower and upper limit of the interval? Answer choices are rounded to the thousandths place.
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Answer:
The Confidence Interval = (0.172, 0.228)
Where:
The lower limit = 0.172
The upper limit = 0.228
Step-by-step explanation:
The formula to be applied or used to solve this question is :
Confidence Interval formula for proportion.
The formula is given as :
p ± z × √[p(1 - p)/n]
n = Total number of red candies = 550 red candles
p = proportion = Number of red candies counted/ Total number of red candies
= 110/550 = 1/5 = 0.2
z = z score for the given confidence interval.
We are given a confidence interval of 90%. Therefore, the z score = 1.6449
Confidence Interval = p ± z × √[p(1 - p)/n]
Confidence Interval = 0.2 ± 1.6449 × √[0.2(1 - 0.2)/550]
= 0.2 ± 1.6449 √0.2 × 0.8/550
= 0.2 ± 1.6449 × 0.0170560573
= 0.2 ± 0.0280555087
Hence, the Confidence Interval = 0.2 ± 0.0280555087
0.2 - 0.0280555087 = 0.1719444913
Approximately = 0.172
0.2 + 0.0280555087 = 0.2280555087
Approximately = 0.228
Therefore, the Confidence Interval = (0.172, 0.228)
Where:
The lower limit = 0.172
The upper limit = 0.228
