I Just Sample It
The sampling distribution is a distribution of all these that are possible for a certain size sample.
What are means?
The critical value for creating the boundaries for the rejection region in a z-test are determined by the number of tails in the test and this.
What is the alpha level?
What is the z-score for a sample with a mean of 6 which is being compared to population with a mean of 9, where the standard error of the mean = 2?
What is z = -1.5?
This measure of effect size tells us the proportion of variability accounted for, and is often used alongside the t-test.
What is r2, or the coefficient of determination?
A researcher would like to examine how the chemical tryptophan, contained in foods such as turkey, can affect mental alertness. A sample of n = 9 college students is obtained and each student’s performance on a familiar video game is measured after eating a traditional Thanksgiving dinner including roast turkey. We compare this to a second sample of students who have their performance measured after eating PB & J sandwiches (almost no tryptophan).
The test you should use is this.
What is an independent samples t-test?
According to the Central Limit Theorem, the shape of the sampling distribution becomes more normally distributed as this increases.
What is the sample size (or N)?
Concluding that a treatment has an effect when it really has no effect is this.
What is a Type I Error?
A researcher conducts a hypothesis test to evaluate the effect of an etiquette class on politeness. The hypothesis test produces the following results: z (65) = -2.60. Assuming that the researcher is using a two-tailed test and alpha of .05, what is the correct decision?
What is reject the null, the etiquette class does have an effect on politeness?
The results of a single-sample t-test (two-tailed, alpha = .05) are reported as follows: t(29) = 2.02. Based on this report, the number of individuals in this study was this, and the correct decision was this.
What is n=30 AND fail to reject the null?
A researcher is interested in testing the itching side effect some people reported when using new Harry's shaving cream. In the general population people scratch their skin μ = 2 times per hour with σ = 0.3. The researcher asks a group of women to use the new shaving cream, and then records how often each woman scratches her legs in an hour.
The test you should use is this.
What is z-test?
As sample size increases, standard error does this.
What is decreases?
The hypothesis that matches onto the researcher's actual hypothesis is called this.
What is the alternate hypothesis?
This reports how many standard deviations above the population mean the sample mean is.
What is Cohen’s D?
In an independent-samples hypothesis test, what does t = 0 tell us about the sample means?
What is that the two population means are equal?
If you are comparing a sample to a population, but you only know the mean of the population (you do not know the population's SD).
The test you should use is this.
What is a single sample t-test?
Researchers want to determine the cuteness of different breeds of puppies, rating them on a scale of 0-30. A sample of pug puppies obtained from a population with σ = 12 points has a σM = 2 points. How many pugs are in the sample?
What is n=36?
When conducting a two-tailed hypothesis test of z, with an alpha = .01, this would be the proportion of scores which fall the rejection region on the right-hand side of the distribution.
What is p = .0050 or 0.5%
When this decision happens, you conclude that there is a significant difference between the two populations (the known population and the unknown population).
What is "reject the null" (AKA p<.05)?
One sample has n = 8 and SS = 21 and a second sample has n = 8 and SS = 35. What is the pooled variance for the two samples?
What is 4?
(21 + 35)/(7 + 7) = 56/14 = 4
You have an independent variable you'd like to manipulate and measure its effect on a dependent variable, but you have no information about any associated populations.
The test you should use is this.
What is an independent samples t-test?
In the general population, the weight of newborn babies is normally distributed with μ = 7.5lbs and σ = 1.25lbs. If you take a random sample of n = 25 newborns, what is the probability that the sample mean would be greater than M = 8lbs?
What is .0228 or 2.28%
std error = 1.25/(sqrt 25) = 1.25/5 = 0.25
z = (8-7.5)/0.25 = 0.5/0.25 = 2
proportion for z = 2 is .0228
When you increase either of these in your study, the power of your study will also go up!
What is sample size or alpha-level?
A sample of 25 lifeguards from Fort Lauderdale are asked to report how many times they have seen dolphins swimming in the ocean this summer, and their mean response = 8.
Researchers first compare this sample to the population of lifeguards in the US which have a mean = 6, standard deviation = 3.
Researchers also compare this sample to the population of life guards in the Dominican Republic which have a mean of 6, standard deviation = 1.
The population comparison with the greatest chance of finding a significant difference is this group.
What is the Dominican Republic population?
This is the range of means, based on our sample information, within which we expect to see the population mean a given proportion of the time.
What is a confidence interval?
We know that the population mean for the number of movies watched at the theater per person per year is 5. We look at a sample of individuals who have a movie subscription service membership (like moviepass) to see if the number is significantly different than that. You find a mean for you sample of n = 40 individuals is M = 6.3, with a SD = .7.
The test you should use is this.
What is a single sample t-test?