1.What would happen to the confidence intervals if you changed the level of confidence? 2.What would happen to the confidence interval if you increase the sample size?
Quinnipiac University Poll is a leading polling organization. In May 2019, it released a survey conducted from May 16 to May 20, 2019 of 1,078 self-identified registered voters. The poll asked a series of questions about a woman’s right to have a legal abortion. Here is question 47: How about when a pregnancy was caused by rape or incest; do you think abortion should be legal in this situation or not? Here are the percentage of respondents, broken out by political affiliation, who support the right of a woman to have an abortion under these conditions.
|
|
Republican |
Democrat |
Independent |
|
Support |
68% |
92% |
83% |
|
|
313 |
345 |
323 |
1.What would happen to the confidence intervals if you changed the level of confidence?
2.What would happen to the confidence interval if you increase the sample size?
The general formula for calculating width of the confidence interval for the population proportuon is,
Here, s is the standard deviation of the sample
From the formula it can be seen that width and critical value is directly proportional to each other. And it is known that as the confidence level increases the critical value also increases, Therefore when the confidence level increases the width of the confidence intervals also increases and vice versa.
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