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40 Cards in this Set
- Front
- Back
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What is a random sample |
When every member of the population has an equal chance of being selected |
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Convenience sample |
Uses participants who are readily available |
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Volunteer sample |
Self selected (bias) |
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What are the sampling methods included in stratified sampling |
Proportionate stratified sample & Disproportionate stratified sample |
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Proportionate stratified sample |
Size of the sample selected from each subgroup is proportional to the size of that subgroup in the the entire population. |
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Disproportionate stratified sample |
The size of the sample selected from each subgroup is disproportional to the size of that subgroup in the population |
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Random Assignment |
All participants have an equal chance of being assigned to a condition. Frequently used. Offsets limitations of convenience sample
*Random selection is almost never used |
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What is Generalizability |
The researcher's ability to apply findings from one sample or one context to other samples or contexts |
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Expected relative-frequency probability |
Likelihood of an event occurring based on actual outcomes of many trials |
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Probability Formula |
P = # of success Divided by # Of Trials
P = Success / # Of Trials |
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Addition Rule Mutually Exclusive Rule
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No two outcomes, e.g., head and tail, can occur simultaneously QUARTER |
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What is the probability of an event not occuring |
1 - p (of the event occurring) , Converse rule 1-P(F) |
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P(A or B) = ? P(either head or Tail) = ? |
P(A) + P(B) P(either Head or Tail) = p(head) + P(tail) |
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Independent Rule When outcomes are independent = Formula?!
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One occurring over and over again does not change the likelihood of the other occurring.
P(A+B)=P(A) x P(B) |
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Example of independent Rule |
Prosecutor working on robbery and kidnap cases. P of getting both convictions is... |
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P of obtaining a combination of independent outcomes = |
Product of their separate P |
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Example of addition rule |
A boy reaches into a big bag of candy to get a piece of candy. The probability of getting gum is .22. Probability of chocolate .26 and the probability of getting taffy is .56. adds up to 1. Probability of getting any candy at all |
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Addition rule formula = |
P(chocolate or taffy) = P(chocolate) + P(Taffy) =.52 +.26 = .78 |
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Multiplication formula (independent outcomes) |
P(A+B) = P(A) x P(B) Prosecutor working on robbery and kidnap cases. P of getting both convictions is..... |
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What is inferential Statistics |
Use of rules of probability to test hypothesis Use of probability to make decisions |
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Hypothesis Testing |
When you use probability with inferential statistics and ask how likely is an outcome? |
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Null Hypothesis Testing |
Proving that there is no difference H 0 (no effect, no change, zero effect, not different, electricity attack on a rock type pokemon)
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Research Hypothesis |
There is a difference H 1 (There is an effect, will be different) |
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Example of H1 or H0 hypothesis testing |
Study of cocaine on recent memory, measured by digit span. Random sample of 64 adult volunteers. Took dosage of coke. Took test M = 7.53 Studies say u = 7, o = 2 . Difference of .53 H0: u = 7 H1: u > 7 there is a difference Null is rejected!! H1's win H1's win!! |
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What is a Type 1 error |
Sins of commision - rejecting the null hypothesis when it is true "saying something happened when it didn't" |
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What is Type 2 error |
Sins of omission - failing to reject the null hypothesis when it is false " Saying that nothing happened when, in fact, it did." |
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What z-score do you need to be in the 75th percentile? |
.68 |
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If on a test you got a z-score of 1.10 because the teacher lost all the test scores. Plus what percentile were you in? What percentage was in the tail? |
13.59% in the tail Then you were in the 86.43 percentile
INVERSE!! |
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To transform raw scores into standard deviation |
You reverse the z score formula (then multiply both sides by the mean if you don't want to deal with all the math) then solve for Z |
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If alpha is 5% then what is the z-score? |
1.96 |
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From 95% to 99% interval. What happens to your interval? What weapon is it like? |
You lose precision, but you are more likely to be accurate and hit the target. From a sniper to a shotgun. MORE SPREAD!!! |
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When alpha is 1% (0.1) . what is the z-score?
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2.58 |
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When is the alpha of 1% used? |
When the CI is 99% |
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What is a confidence interval? |
Estimating a specific interval that a score will land in? -a Range -Always for the mean |
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What does a 99% confidence level mean? |
If the experiment is repeated 100 times then 99 of it will fall into the interval. |
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What is statistical power of a test |
Means there is a difference in the world and you are rejecting the Null. |
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How to increase the power of a test? |
Increase the N (sample) The alpha level increased. |
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Confidence interval formula |
M +/- Z(standard error) add to get upper boundary, Subtract to get lower |
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WHAT IS COHENS D?? |
How big of a difference is there? If .2 small diff. If bwtn .2 and .8 its a medium sized difference. |
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Whats the mean of a Standard Normal Distribution, and the empirical rule on it. |
The mean is 0 16%, 68%, 16% |
