Confidence Intervals: Statistical Techniques

What are confidence intervals?

• a.Confidence intervals tell you the mean and standard deviation of a subsample.
• b.Confidence intervals tell you precisely the value of an unknown parameter.
• c.Confidence intervals use subsample statistics, like the mean and standard deviation, to provide a range of values to estimate an underlying parameter.
• d.Confidence intervals tell you which confidence level to apply to the data.

You should use a t-distribution to estimate the population mean in the following situation:

• a.The subsample size is small and the population’s standard deviation is unknown.
• b.The subsample size is large and the population’s standard deviation is unknown.
• c.The subsample size is small and the population’s standard deviation is known.
• d.The subsample size is large and the population standard deviation is known.

The lower the confidence level, the more uncertainty is associated with the estimation.

• a.true
• b.false

You would like to calculate the standard error of the mean for a subsample where the standard deviation (s) is 0.010 and the subsample size (N) is 16. Using the equation [standard error of the mean = s/sqrt N], which is the correct answer?

• a.0.00625
• b.0.0025
• c.0.25
• d.0.0625

While reading a scientific journal article, you note that the researchers chose a confidence level of 99% for the confidence intervals of their population mean. What does a 99% confidence level tell you?

• a.There is a 99% chance the population mean lies within their stated confidence intervals.
• b.The confidence intervals contain 99% of the population mean distribution.
• c.99% of the confidence intervals for subsamples from the same population include the population mean.
• d.Only 1% of the subsamples were outside the population mean.

All of the following are acceptable confidence levels EXCEPT

• a.90%
• b.95%
• c.99%
• d.100%

While collecting data on fruit fly wing sizes you find one subsample with a much larger spread, or variation, among the data points compared to other subsamples. Compared to the other subsamples and using the same confidence level, this one’s confidence interval range will be

• a.larger.
• b.smaller.
• c.the same.
• d.None of the above

Confidence intervals

• a.are the only technique researchers use to make inferences about subsamples.
• b.help scientists to make precise inferences about their data.
• c.are used by scientists to summarize the information about a subsample.
• d.allow a researcher to infer how a single experiment relates to a larger population or phenomenon.