# Is a 95% confidence interval wider than a 90% confidence interval?

A 99 percent confidence interval would be wider than a 95 percent confidence interval (for example, plus or minus 4.5 percent instead of 3.5 percent). A 90 percent confidence interval would be narrower (plus or minus 2.5 percent, for example).
A.

### What is the effect of increasing the level of confidence on the width of the interval?

Increasing the sample size decreases the width of confidence intervals, because it decreases the standard error. c) The statement, "the 95% confidence interval for the population mean is (350, 400)", is equivalent to the statement, "there is a 95% probability that the population mean is between 350 and 400".
• #### What is the significance of the width of the confidence interval?

Increasing the sample size decreases the width of confidence intervals, because it decreases the standard error. c) The statement, "the 95% confidence interval for the population mean is (350, 400)", is equivalent to the statement, "there is a 95% probability that the population mean is between 350 and 400".
• #### What is the confidence interval in statistics?

In statistics, a confidence interval (CI) is a type of interval estimate, computed from the statistics of the observed data, that might contain the true value of an unknown population parameter. Most commonly, the 95% confidence level is used.
• #### What is the margin of error in statistics?

The margin of error for a particular statistic of interest is usually defined as the radius (or half the width) of the confidence interval for that statistic. The term can also be used to mean sampling error in general.
B.

### What is a good 95% confidence interval?

If repeated samples were taken and the 95% confidence interval was computed for each sample, 95% of the intervals would contain the population mean. A 95% confidence interval has a 0.95 probability of containing the population mean. 95% of the population distribution is contained in the confidence interval.
• #### What is the z score for 99 confidence interval?

Confidence Intervals
Desired Confidence IntervalZ Score
90% 95% 99%1.645 1.96 2.576
• #### How do you know if a confidence interval is significant?

So, if your significance level is 0.05, the corresponding confidence level is 95%.
1. If the P value is less than your significance (alpha) level, the hypothesis test is statistically significant.
2. If the confidence interval does not contain the null hypothesis value, the results are statistically significant.
• #### How can the width of a confidence interval be reduced?

1. Increase the sample size. Often, the most practical way to decrease the margin of error is to increase the sample size.
2. Reduce variability. The less that your data varies, the more precisely you can estimate a population parameter.
3. Use a one-sided confidence interval.
4. Lower the confidence level.
C.

### How can the width of a confidence interval be reduced?

1. Increase the sample size. Often, the most practical way to decrease the margin of error is to increase the sample size.
2. Reduce variability. The less that your data varies, the more precisely you can estimate a population parameter.
3. Use a one-sided confidence interval.
4. Lower the confidence level.
• #### What is the significance of the width of the confidence interval?

Increasing the sample size decreases the width of confidence intervals, because it decreases the standard error. c) The statement, "the 95% confidence interval for the population mean is (350, 400)", is equivalent to the statement, "there is a 95% probability that the population mean is between 350 and 400".
• #### What happens to the margin of error if you increase the confidence level?

Answer: As sample size increases, the margin of error decreases. As the variability in the population increases, the margin of error increases. As the confidence level increases, the margin of error increases.
• #### Why are some confidence intervals wider?

Apparently a narrow confidence interval implies that there is a smaller chance of obtaining an observation within that interval, therefore, our accuracy is higher. Also a 95% confidence interval is narrower than a 99% confidence interval which is wider. The 99% confidence interval is more accurate than the 95%.

Updated: 3rd December 2019