Exam #1: Biostatistics III Flashcards
What is a sampling distribution?
The probability distribution of the statistic
What is an unbiased estimate of the parameter?
When the mean of the sampling distribution of a statistic can be shown to be equal to the parameter being estimated
What is a biased estimate of the parameter?
When the mean of the sampling distribution is NOT equal to the parameter
What is the formula for standard deviation of the sampling distribution?
Standard deviation of sampled population/ square root of the sample size
What is another name of the standard deviation of the sampling distribution?
Standard error of the mean
What is z?
Standard normal statistic
Write the formula for z.
Sample mean - population mean/ standard error of the mean
What is the central limit theorem?
With a sufficiently large random sample, the distribution will be normal
In the central limit theorem, what happens as the sample size gets larger?
Sample distribution becomes almost normal
What is the sample statistic in a confidence interval?
Point estimate around which the upper and lower confidence limits are set
What is a confidence interval for a population mean?
A range of plausible values for the population mean
Write the formula for calculating the confidence interval.
N/A
What is the margin of error for 95% confidence?
1.96
What is the margin of error for 99% confidence?
2.58
What happens to the area under the curve with a higher confidence interval?
Gets larger
What does a 95% confidence interval mean?
- 95% of the confidence intervals will contain u
- 5% will NOT
What conditions need to be satisfied for a valid confidence interval?
- Random sample
- n must be large
What is the difference between the standard normal statistic (z) and t-statistic?
S replaces the population standard deviation
What are degrees of freedom?
- Variability in the sampling distribution of t depends on the sample size, n
- A way of expressing this is the “degrees of freedom”, calculated as (n-1)
What can the sampling error be used to determine?
Necessary sample size to have a specific margin of error/ confidence
What is a statistical hypothesis?
A statement about the numerical value of a population parameter
What is the null hypothesis?
Hypothesis that will be accepted unless the data provides evidence it is false
What is the alternative hypothesis?
Hypothesis that will be accepted only if the data provide evidence it is true
Write the three ways of stating the alternative hypothesis.
N/A
When do we use hypothesis testing?
1) Observational studies
2) Clinical trials
What is a test statistic?
- A sample statistic
- Used to decide between null and alternative hypothesis
What is a Type I Error?
- Null hypothesis rejected when it is in fact correct
- Denoted as alpha
What is a Type II Error?
- Accepting the null hypothesis when the alternative hypothesis is correct
- Denoted as Beta
What is the rejection region?
Set of possible values of the test statistic for which the researcher will reject null in favor of alternative
What happens if a test statistic falls in the rejection region?
Reject the null hypothesis and accept the alternative
What is a p-value in a hypothesis test?
Observed significance level
- Probability of observing a value of test statistic that is at least as contradictory to the null hypothesis as the actual one computed from sample data
