L5 - Descriptive Statistics Flashcards
1
Q
Why do descriptive Statistics
A
- Describe the general characteristics of the sample
- Where data was collected
- In sample, mean and age
2
Q
What are the different types of variables?
A
3
Q
What are categorical variables?
A
- Found in SPSS frequencies
- Nominal and ordinal variable
- useful to know how many cases belong to each category group
- Due to statistical tests requiring 10+ cases
- To produce reliable results
4
Q
What are continuous variables?
A
- Scale level measures
- Age, weight, number of errors
- Compromises a large number of distinct values
- Therefore little sense to look at frequency tables
- Better for summary statistics like normality and dispersion
5
Q
Why do you need measures of variablility?
A
- Variability - How much the data values differ from the mean
- Mean is not suffice due to variability
- Range, SD (noral distrabution = 68%)
6
Q
What is standard deviation?
A
- Average Difference of values from sampler mean
- Bigger = greater difference
- Normal distribution = 68% of values lie within 1 SD of the mean
7
Q
What is normal distrabution?
A
8
Q
Kurtosis - Measures of Normality
A
- Important to check for deviations from normal distribution
- Bigger kurtosis = only a problem for smaller samples (<200)
9
Q
What is skewness?
A
Skewness - Measures of Normality
- The symmetry of distribution
- Positive skew - more low values than expected
- Negative skew - more high values than expected
- Can be used to gage the difficulty of exams
