1.3 psychology statistics
DESCRIPTION
1.3 Psychology Statistics. AP Psychology Mr. Loomis. Descriptive Statistics. Definition… Describe a set of data Measures of Central Tendency Measures of Variation Skewed Distributions. Measures of Central Tendency. Mean Average score - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/1.jpg)
1.3 Psychology Statistics
AP PsychologyMr. Loomis
![Page 2: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/2.jpg)
Descriptive Statistics
• Definition…• Describe a set of data
• Measures of Central Tendency• Measures of Variation• Skewed Distributions
![Page 3: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/3.jpg)
Measures of Central Tendency
• Mean – Average score– Extreme scores have a greater impact on the mean than
on the mode or median• Median– Score that divides a frequency distribution exactly in
half, so that the same number of scores lie on each side (middle)
• Mode– Most frequently occurring score (bimodal)
![Page 4: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/4.jpg)
![Page 5: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/5.jpg)
![Page 6: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/6.jpg)
![Page 7: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/7.jpg)
Measures of Variation
• Definition– Measure of variation in a single score that presents
info about the spread of scores in a variation• Range – highest minus the lowest• Standard Deviation – a standard measurement of
how much the scores in a distribution deviate from the mean– The most widely used measure of variation
• Z-score (standard score) – the distance of a score from the mean in units of standard deviation
![Page 8: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/8.jpg)
![Page 9: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/9.jpg)
Normal Distribution
• Form a bell-shaped or symmetrical curve
![Page 10: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/10.jpg)
Normal Distribution
• The percentage of scores that fall at or above the mean is 50…the percentage that fall below (or at) the mean is also 50
![Page 11: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/11.jpg)
Normal Distribution
• On-third of the scores fall one standard deviation below the mean and on-third fall one standard deviation above the mean
• Example…Wechsler IQ Tests– Mean = 100 / Standard Deviation = 15– One-third score 85-100– Another third score 100-115
![Page 12: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/12.jpg)
![Page 13: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/13.jpg)
68-95-99.7 Rule• 68% of scores fall within one SD • 95% of scores fall within two SD• 99.7% of scores fall within three SD
![Page 14: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/14.jpg)
Percentile• Distance of a score from “0”• Examples– 90th percentile – score better than 90%– 38th percentile – score better than 38%
![Page 15: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/15.jpg)
![Page 16: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/16.jpg)
Skewed Distributions
![Page 17: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/17.jpg)
Skewed Distributions• Positively Skewed Distributions• Contain a preponderance of scores on the low
end of the scale (looks like “P” lying on back• Mean is higher than the median– Thus the median is a better representation of
central tendency in positively skewed distributions
![Page 18: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/18.jpg)
Skewed Distributions• Negatively Skewed Distributions• Contain a preponderance of scores on the
high end of the scale• Mean is lower than median– Thus the median is a better representation of
central tendency in a negatively skewed distribution
![Page 19: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/19.jpg)
![Page 20: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/20.jpg)
![Page 21: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/21.jpg)
Inferential Statistics
• Key points…• Most experiments are conducted with a small
sample of subjects• Psychologists want to generalize the results from
their small sample to a larger population• IS are used to determine how likely it is that a
study’s outcome is due to chance and whether the outcome can be legitimately generalized to the larger population from the sample selected
![Page 22: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/22.jpg)
![Page 23: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/23.jpg)
![Page 24: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/24.jpg)
The P-Value
• Probability of concluding that a difference exists when in fact this difference does not exist
• A statistically significant difference is a difference not likely due to chance (shows up 5% of the time or less)
• Smaller the p-value, the more significant the results
• Can never be “0” (researchers can never be 100% certain the results did not occur by chance)
![Page 25: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/25.jpg)
![Page 26: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/26.jpg)
![Page 27: 1.3 Psychology Statistics](https://reader030.vdocuments.site/reader030/viewer/2022020210/56816711550346895ddb7989/html5/thumbnails/27.jpg)