1 / 15

AP Psychology

AP Psychology. Inferential Statistics Sampling and Selection. Essential Question. 1-5 How do psychologists draw appropriate conclusions about behavior from research?. Inferential Statistics. You are trying to reach conclusions that extend beyond the immediate data alone.

dot
Télécharger la présentation

AP Psychology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. AP Psychology Inferential StatisticsSampling and Selection

  2. Essential Question • 1-5 How do psychologists draw appropriate conclusions about behavior from research?

  3. Inferential Statistics • You are trying to reach conclusions that extend beyond the immediate data alone. • Used to test hypothesis about samples.

  4. Testing for Differences • If we have results from two samples we can ask the question: • Is there a difference between • the means of the two the samples?

  5. Testing for Differences • Using the assumption of a normal distribution, we can also ask the question: • How confident are we that the mean difference is genuinely represented in the population rather than just due to random variation? • Using inferential statistics, we can ask this question using a t-test when comparing two groups.

  6. P values and statistical significance • Generally, the t test gives a P value that allows us a measure of confidence in the observed difference. • It allows us to say that the difference is real and not just by chance. • The smaller the p value the least chance of making a false positive (Type I error). • A p value of less than 0.05 is a common criteria for significance. • We call this statistically significant

  7. An Example Experiment • Does caffeine improve our reaction time? • We recruit 40 people and give • 20 a cup of coffee • 20 a cup of decaffeinated coffee • We give them a brief reaction time test and record the results.

  8. Inferential Statistics • Caffeine condition • Mean = 500.32ms • SD = 172.60ms • No Caffeine condition • Mean = 608.64ms • SD = 146.93

  9. Effect of Caffeine on RT? Caffeine No Caffeine

  10. t-test results • Does caffeine improve our reaction time? • Caffeine condition has a lower mean RT. • We run a t-test on our samples and get: • p = 0.039 • Can we be confident that the difference in the data is not due to chance? (P Value video) • ANOVA An ANOVA (Analysis of Variance), sometimes called an F test, is closely related to the t test. The major difference is that, where the t test measures the difference between the means of two groups, an ANOVA tests the difference between the means of two or more groups.

  11. Video notes • 1) P value refers to the likelihood your research results were by chance. It usually has to be below .05 for the differences you found to have any real meaning. • 2) F critical is the value that must be "crossed" in order for p value to be significant. • 3) If F critical is passed, then the p value gets glory (so to speak) because it is now significant. • 4) Bonferroni is a conservative stats adjustment used when making many comparisons between effects. it makes it more likely that p will be non-significant and that F critical will not "have her threshold" crossed.

  12. Condition 2: Sleep Deprived Condition 1: Slept Well Time Test memory Test memory again Within / Between Group Comparison • Two ways of comparing people: • Within groups (everybody does all conditions) • e.g. ‘before and after’ study

  13. Group 2: Females Group 1: Males Test visual abilities Test visual abilities Within / Between Group Comparison • Between groups (different people do each condition) • e.g. ‘males vs females’ study

  14. Summary • Descriptive statistics give a summary of the data. • Statistical dispersion describes the spread of the data. • Many attributes are normally distributed. • Inferential statistics allow us to test hypotheses using this assumption. • Studies need to be carefully designed to make this meaningful.

  15. Essential Question • 1-5 How do psychologists draw appropriate conclusions about behavior from research?

More Related