Study of sex differences among drivers in two countries (USA & Greece)
Other names =
What do they do?
AKA confound, covariate, or 3rd variable
Affects DV. but is not an IV
Can bias study, lead to wrong conclusion
Ultimately has affect on IV
(IV STIMULUS --> DV RESPONSE --> Confounding variable --> IV STIMULUS)
Examples of covariates
Whats the order
Date -> ______ ->
Data, statistical analysis, Information
What are the two types of statistics?
Best way to describe a variable is?
Summarize/Describe the data from your study (the sample)
Goal:Try to summarize data with two numbers without sacrificing crucial data:
Average = Signal
Variability = Noise
Best way to describe a variable is by its type (nominal, ordinal, etc) and distribution
Are used to make predictions/inferences about the population based on the sample
Single value most typical of all data
Mode = Most freq value
Works best for what distribution?
Used to describe?
Okay for what types of data?
-Most freq value
-Works best for unimodal distribution
-Used to describe average of nominal variable
-Okay for what types of data:
(Ordinal Interval or Ratio)
APA format =?
Apa = Mdn
Divide Data in half ( 125 )
Used to describe which data?
Mean = Best guess
average of interval or ratio variables, but only if distribution is unimodal and symmetric (not skewed)
IF distribution is unimodal and symmetric
Mode = Mdn = M
If distribution is unimodal with positive skew:
Mode < Mdn < M if unimodal
Would you report Mean, Median, or Mode?
Test Score (0-50)- Normal Distribution
Test score (0-50)- Highly Skewed Distribution
Temperature-- Normal Distribution
SIze of dog (small, medium, large)
Exam Grades (A, B, C, D, F)
INcome under (10k, 10-20k, 20-30 etc)
Eye ColorTest Score (0-50)- Normal DistributionTest score (0-50)- Highly Skewed DistributionTemperature-- Normal DistributionSIze of dog (small, medium, large)Exam Grades (A, B, C, D, F)INcome under (10k, 10-20k, 20-30 etc)
What is mean, median, mode of
Mode = 1
Which would u use? Mean median mode
Does average completely describe the data?
No, because two distributions can have same average but look very different.
Need at least one other descriptive statistic.
*Single most typical difference from average
*Need to describe how much scores differ from average (ho wmuch noise is present)
Often used for?
Variabilities: How to measure them?
Interquartile Range- Middle half of scores
25th - 75th percentile
Range = Largest datum - smallest datum
where Q3 is the median of the upper half and Q1 is the median of the lower half of data. Q2 is the median of all data
Squared Standard Deviation
Standard Deviation =
Mean deviation from M, ignoring sign (sort of)
Different Mean =
Same Mean =
Different Mean =
Different Mean = Same SD
Same Mean = Different SD
Different Mean = Different SD
Descriptive Statistics to report in Method Section/Participant subsection
Sex: # of M & # of F
Age: Min, Max, and either M and SD (of symmetric) or Mdn and IQR range (of skewed)
Other key demographics such as ethnicity if important
Descriptive Statistics of DV to report in...
If DV is nominal or ordinal with few levels:
Mode for each cell
If DV is ordinal, or interval/ratio and skewed: n, Mdn, and IQR rang for each cell
If DV is interval/ratio and symmetric: n, M, and SD for each cell