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Subscription fee for a writer who signs up = $ 5
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Number of subscribers who left the website = 10
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Now, total subscription fee received this month =
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Answer:
The margin of error M.O.E = 2.5%
Step-by-step explanation:
Given that;
The sample size = 1500
The sample proportion = 0.60
Confidencce interval = 0.95
The level of significance ∝ = 1 - C.I
= 1 - 0.95
= 0.05
The critical value:
(From the z tables)
The margin of error is calculated by using the formula:
M.O.E = 0.02479
M.O.E ≅ 0.025
The margin of error M.O.E = 2.5%
Answer:
a) 25% of the students exam scores fall below 55.6.
b) The minimum score for an A is 84.68.
Step-by-step explanation:
Normal Probability Distribution:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean and standard deviation
, the z-score of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
Mean of 61 and a standard deviation of 8.
This means that
(a) What score do 25% of the students exam scores fall below?
Below the 25th percentile, which is X when Z has a p-value of 0.25, that is, X when Z = -0.675.
25% of the students exam scores fall below 55.6.
(b) Suppose the professor decides to grade on a curve. If the professor wants 0.15% of the students to get an A, what is the minimum score for an A?
This is the 100 - 0.15 = 99.85th percentile, which is X when Z has a p-value of 0.9985. So X when Z = 2.96.
The minimum score for an A is 84.68.