In a certain neighborhood there are 25 dogs and 10 cats. In a neighborhood across the way, the ratio of cats to dogs is the same
1 answer:
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Answer:
The sample size is 1875.
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of , and a confidence level of
, we have the following confidence interval of proportions.
In which
z is the zscore that has a pvalue of .
The margin of error is:
Sampling error of 0.03.
This means that
99.74% confidence level
So , z is the value of Z that has a pvalue of
, so
.
25% of all adults had used the Internet for such a purpose
This means that
What is the sample size
The sample size is n. So
Simplifying by 0.03 both sides
The sample size is 1875.
Answer:
(B) The standard normal variable Z counts the number of standard deviations that the value of the normal random variable X is away from its mean
Step-by-step explanation:
Problems of normally distributed samples are solved using the z-score formula.
In a set with mean and standard deviation
, the zscore 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 pvalue, we get the probability that the value of the measure is greater than X.
Positive z-score: Above the mean
Negative z-score: Below the mean
All variables are continuous.
X can be positive or negative, just like Z
So the correct answer is:
(B) The standard normal variable Z counts the number of standard deviations that the value of the normal random variable X is away from its mean