PSYC 2260 Lecture Notes - Lecture 3: Statistic, Statistical Parameter, Standard Score
26 Jun 2018
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PSYC 2260 Introduction to Research Methods in Psychology
Chapter 3 Some Key Ingredients of Inferential Statistics
Z Scores
A raw score converted to standard deviation units
Uses:
1. To describe where a particular score is located in a distribution
2. To compare scores on different measures
E.g. Mean height = 68”; SD = 6 Mean weight = 150 lb; SD = 15
An individual’s height 65” and weight 130lb, is he closer to average on height or
weight?
Z for height = -1.33; Z for weight = -0.5
Important concept:
- Any distribution of Z scores always has: mean = 0; SD = 1
- No matter what the original scale of measurement. For this reason, Z is often called a
“standard score”
The Normal Curve Table used to determine:
“area under the curve”
% of Z
Z of %
E.g. a person with a Z-score = -.50 Using table: look up .5 = 19.15%
Brief note about probability = “p”
The expected relative frequency of a particular outcome:
P =
Long-run relative-frequency interpretation of probability: understanding of probability as the
proportion of a particular outcome that you would get when repeated many times
-Expected relative frequency: number of successful outcomes divided by the number of total
outcomes you would expect to get if you repeated an experiment a large numbers of times
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