Confidence Intervals
What does a confidence interval estimate?
What is a population parameter?
The null hypothesis is typically a statement of this.
What is no effect or no difference?
The value we estimate using a sample.
What is a parameter?
Interpret a 90% confidence interval from 12.1 to 15.3.
What is we are 90% confident the confidence interval of 12.1 to 15.3 captures the parameter
Formula for standard error of a sample mean.
A 95% confidence interval means this.
What is we expect 95% of such intervals to contain the true parameter?
The probability of observing a result as extreme or more extreme than the one observed, assuming the null is true.
What is the p-value?
The statistic that estimates the population proportion.
What is p^?
If a 95% CI for a mean is 10 ± 2, this is the margin of error.
What is 2?
The z* value for a 95% confidence level.
What is approximately 1.96?
Increasing the confidence level does this to the interval.
What is makes it wider?
If the p-value is less than α, we do this.
What is reject the null hypothesis?
This term describes a sampling method where the population is divided into homogeneous groups, and a random sample is taken from each group.
What is stratified random sampling?
If the null value is outside the confidence interval, we do this in a significance test.
What is reject the null hypothesis?
You survey 100 people and find p^=0.6. Give the standard error.
What is square root of (.6)(.4)/100=0.049
What are the conditions before calculating a confidence interval for a mean.
Random sampling, 10% condition, and CLT
The two types of errors in significance testing.
What are Type I and Type II errors?
This term refers to the value that separates the higher half from the lower half of a data set and is not affected by extreme values.
What is the median?
A regression analysis of the relationship between hours studied and exam score gives an r^2 value of 0.87. Interpret this value in context.
What is: About 87% of the variability in exam scores can be explained by the linear relationship with hours studied?
What affects margin of error besides confidence level?
What is sample size and standard deviation?
The formula for a confidence interval for a population proportion.
What is p^ +- z square root of p^(1-p^)/n
The steps in conducting a significance test (list at least three).
What are: State hypotheses, check conditions, calculate test statistic, find p-value, make a conclusion?
The margin of error does NOT account for this confounding variable.
What is bias?
How would you start to write a conclusion for a confidence test with the p-value of 0.04 with an alpha level of 0.05?
What is since the p-value of 0.04 is less than the significance level of 0.05, we reject the null hypothesis.
True or false: A larger sample size results in a smaller standard error.
What is true?