Class notes
Methods in Psychological Research Unit 04
- Course
- PSYB70
- Institution
- University Of Toronto (U Of T )
Unit 04 lecture notes and practice questions
[Show more]
Seller
Follow
Content preview
Evaluating Association ClaimsUnderstanding Statistical Significance
➔ significance testing
◆ decide what decision rules to use to test hypothesis prior to analyzing data
◆ null hypothesis significance testing (NHST): set ofdecision rules that help researcher
use margin of error to determine if observed effect is extreme enough to “reject the
null” and conclude the researcher’s alternative hypothesis issupported(never proved)
➔ statistically significant
◆ an effect is observed, even after factoring in the margin of error
◆ not statistically significant if margin of error is large that it questions whether the
effect exists or not
➔ what is an effect
◆ specific outcome being tested
◆ group comparisons: type of effect that compares twoor more groups
◆ correlation: type of effect that examines the associationbetween variables
➔ to test significance of an effect, start with the assumption that no effect exists (null
hypothesis)
◆ opposite of what the researcher’s hypothesis of there being an effect
◆ null = no effect ; alternative (researcher’s hypothesis) = effect
➔ general approaches for testing significance
◆ confidence interval approach
◆ p-values approach
Confidence Interval Approach
➔ construct a confidence level around the effect (hand calculations or computer program)
◆ i.e. mean difference or correlation coefficient
➔ assess whether the confidence interval around effect includes zero
◆ no zero, results are statistically significant
● fail to reject the null
● researcher hypothesis not supported
◆ yes zero, results arenotstatistically significant
P-Values Approach
➔ 1. set significance level
◆ similar to confidence level
◆ identified using confidence level
● remainder of confidence level = significance level
○ i.e. 95% confidence = 5% significance
, ◆ alpha
➔ 2. calculate effect and p-value
◆ either hand calculations or computer program to calculate effect and probability value
of an effect that large occurring if the effect were actually zero
● the probability value = p-value
➔ 3. compare p-value to statistical significance
◆ if probability value of the effect that large would occur if the effect was actually zero is
lower than the significance level, the results are statistically significant
◆ p-value < alpha = statistically significant
● reject the null
● take next steps to explore hypothesis
◆ p-value > alpha = not statistically significant
● fail to reject the null
● alternative hypothesis not supported
➔ though two approaches were presented, they are rooted in the same foundation
◆ one can be used to make inferences about the other
Understanding Effect Size
➔ considers the size of the group difference and/or strength of the association
➔ Cohen’s d = effect size used to compare the means across two groups
◆ small = |.20|
◆ medium = |.50|
◆ large = |.80|
➔ most effects in psychology are small to medium
◆ rarely large effects
◆ meaning subtle differences rather than huge
➔ power analysis: calculates the ideal sample size forthe effect to be large/seen
◆ larger sample = <statistical error
Cautions of Statistical Significance
➔ only tells if effect is likely to differ from zero in the population that the sample represents
➔ doesn’t say anything about effect size
◆ in large sample sizes, small effect sizes can be significant
➔ not reliable when sample size is low
➔ data from samples are merely estimates of true population parameters…always at risk of
making an error
Two Types of Statistical Error
➔ Type 1 error (false positive)
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller sobikaaravi. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for CA$7.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
50990 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 15 years now