sampling&surveys
What is a simple random sample?
A sample where every group of the same size has an equal chance of being selected.
what does it mean for two events to be independent?
one event does not affect the probability of the other.
what does a confidence interval estimate?
a population parameter
what is the null hypothesis?
a statement that there is no effect or no difference
what does correlation measure?
the strength and direction of a linear relationship between two variables
what type of bias occurs when people choose themselves to participate in a survey?
Voluntary response bias
if P(A)=0.5 and P(B)=0.2, what is P(A and B) if the events are independent?
0.1
what happens to margin of error when sample size increases?
margin of error decreases
what is a p-value?
The probability of getting results as extreme as the sample results, assuming the null hypothesis is true
what does a positive correlation mean?
as one variable increases, the other variable also tends to increase
why is random assignment important in an experiment?
it helps create similar groups and reduces confounding variables
what does a normal distribution look like?
a symmetric bell-shaped curve
when should you use a t-interval instead of a z-interval?
when estimating a population mean and the population standard deviation is unknown.
when do we reject the null hypothesis?
when the p-value is less than the significance level
y^=a+bx
what is the difference between a population and a sample?
a population is the entire group, while a sample is smaller group taken from the population
what is the complement rule?
P(not A)= 1- P(A)
what does "95% confidence" actually mean?
about 95% of intervals from repeated samples would capture the true parameter
what is a Type I error?
rejecting a true null hypothesis
what does the slope of a regression line represent?
the predicted change in y for each 1-unit increase in x
a school surveys only students in AP classes about homework time. why might this sample be biased?
AP students may spend more time on homework than the average student, so the sample is not representative.
A coin is flipped 5 times. What is the probability of getting all heads?
(1/2)^5=1/32
would a 99% confidence interval be wider or narrower than a 90% confidence interval?
wider
a test gives p=0.03 and a=0.05. what decision should be made?
reject the null hypothesis
what is an outlier, and why can it be important in regression?
an outlier is a value far from the others, and it can strongly affect the regression line and correlation.