Vocabulary
The key distinction between experiments and observational studies is whether or not _____ are assigned
Treatments
The probability of pulling a person who does not consume 5+ servings and is 55 or older
3692/8866 = 0.416
z tests are for _______, t tests are for ________
Compare the shapes
Both region A and region B are skewed right
Samples should be _______ of the population from which they are chosen
Representative
The probability of being 18-34, given that the response was no.
741/6675 = 0.111
If p-value is less than 0.05, we ____ Ho and _____ for Ha
reject; have evidence for
Compare the centers
The median lead level in Region B (between 100-150 ppm) is higher than the median lead level in Region A (between 50-100 ppm)
A variable that may influence both the explanatory and response variables in an observational study and "mess up" the results
Confounding variable
Which age group is more likely to say yes: 18-34 or 35-54?
18-34: since 231 / 972 = 0.237, but 669/2911 = 0.229
When constructing a 95% confidence interval for a proportion, these are the three conditions that must be checked
(1) random sample
(2) n*phat and n(1-phat) are at least 10 ("successes and failures"
(3) Population size is at least 10 times sample size
The range of lead levels is APPROXIMATELY 350 ppm (or NO MORE THAN 350 ppm)
The probability of observing a sample result as extreme as the one we observed, given that the null hypothesis is true
P-value
50 people are selected at random from the survey participants. Let X be the number of people who are 55 or older and said "no." X is a _________ random variable with n = ___ and p = ______
Binomial ; n = 50 ; p = 0.416 (3692/8866)
If we fail to reject Ho, but Ho was actually false, we have made this
Type II Error
Do there appear to be any unusual features?
Possible outliers in both graphs; gap between 250-350 in Region B