The weight values for the lower and upper ends of the confidence interval are 192 and 204

# The weight values for the lower and upper ends of the confidence interval are 192 and 204

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The weight values for the lower and upper ends of the confidence interval are 192 and 204 (see  Figure 1). A confidence interval is usually expressed by two values enclosed by parentheses, as in  (192, 204). Another way to express the confidence interval is as the point estimate plus or minus a  margin of error; in this case, it is 198 ± 6 pounds. You are 90 percent certain that the true population  mean of football player weights is between 192 and 204 pounds.  What would happen to the confidence interval if you wanted to be 95 percent certain of it? You would  have to draw the limits (ends) of the intervals closer to the tails, in order to encompass an area of  0.95 between them instead of 0.90. That would make the low value lower and the high value higher,
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Unformatted text preview: which would make the interval wider. The width of the confidence interval is related to the confidence level, standard error, and n such that the following are true: • The higher the percentage of confidence desired, the wider the confidence interval. • The larger the standard error, the wider the confidence interval. • The larger the n, the smaller the standard error, and so the narrower the confidence interval. All other things being equal, a smaller confidence interval is always more desirable than a larger one because a smaller interval means the population parameter can be estimated more accurately. Figure 1. The relationship between point estimate, confidence interval, and z-score....
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