Unformatted text preview: to make inferences about… on the basis of a [email protected] sample Sample: a part of the [email protected] for which a researcher collects data and knows a set of scores 10 9/10/13 Why do we study samples, rather than a [email protected]? [email protected] Goal is to make [email protected] or [email protected] about events beyond our reach Try to study a sample of people who are [email protected] of the [email protected] of interest Random [email protected] is ideal From the full [email protected] of interest, randomly select individuals to be included in sample OCen is [email protected] or impossible to obtain a truly random sample ▪ Instead, try to get a sample that is not [email protected] [email protected] of [email protected] in any known way ▪ Avoid haphazard [email protected] [email protected]@cal terminology varies for sample [email protected]@cs versus [email protected] parameters Population Parameter Sample Statistics Scores from entire population Scores of sample only (Usually unknown) (Calculated from known data) µ (mu) M σ (sigma) SD (sigma squared) SD 2 Mean
Standard
Deviation
Variance σ2 11 9/10/13 Probability deﬁ[email protected]: Expected [email protected] frequency of an outcome Outcome: result of experiment/[email protected] Frequency: how many @mes something happens [email protected] frequency: number of @mes something happens [email protected] to the number of @mes it could have happened Expected [email protected] frequency: what you expect to get in the long run if you repeat the experiment/[email protected] many @mes Long
run [email protected] frequency [email protected] of probability vs. [email protected] [email protected] of probability Probability = Possible successful outcomes All possible outcomes What is the probability of genng a 4 when you roll a die? 1/7 = 0.14 What is the probability of choosing a heart from a deck of cards? 13/52 = 1/4 = 0.25 Range: 0 to 1, also represented 0
100% Probability as the likelihood of occurrence Impossible to Certain 12 9/10/13 Probability is symbolized as the le]er p, and usually represented as a decimal (0 to 1) rather than a percent p = .5 represents a 50/50 chance p < .05 represents “the probability is less than .05” The normal [email protected] can be thought of as a probability [email protected] 15 70 85 100 115 130 You apply to 20 graduate programs, 10 of which are in clinical psychology, 5 of which are in counseling psychology, and 5 of which are in social work. You get a message from home that you received a le]er from one of the programs. Give the [email protected] that it is from A clinical psychology program. A counseling psychology program. From any other program besides social work. 13 9/10/13 A student wants to study the eﬀect of stress on memory. He posts a sign
up sheet for anyone willing to [email protected] The student is [email protected]: a. Random [email protected] b. Haphazard [email protected] c. Speciﬁed [email protected] d. Quota [email protected] In [email protected]@cal language, a scoop of water drawn from a ﬁsh tank full of tropical saltwater ﬁsh to determine the exact salt content of the water is: a. [email protected] b. Parameter c. Sample d. [email protected] [email protected] In a normal curve, approximately __?__ percentage of scores are lower than 2 standard [email protected] below the mean. In a normal curve, approximately 68% of the scores are between a z
score of __?__ and a z
score of __?__. In a normal curve, what percentage of scores fall within 2 standard [email protected] of the mean? 14...
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 Winter '13
 bernard
 Psychology, 14%, 98%, 34%, 68%, 84%, 96.25%

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