L2 - Descriptive Statistics

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1. Frequency Distributions --> histogram! is the data distributed?

TAIL NEGATIVE = NEGATIVE SKEW!!!

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Central Tendency - where is the middle??

mean mode median!

which one best represents the middle?

Mean = add em up and divide by total number of scores!

Median = mid point of the distribution

Mode = MOST common value!

Normal distribution same median, mode and mean!

Mean is the best measure but once skewed median is better measure!

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Variability!

Range --> some problems with if data is mostly clumped at the ends of the range

Variance!

Deviations -->

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Inferential Statistics

- Correlation

- T-test

What is the role of inferential statistics?

- we draw inferences abou the population using observations of the sample data

test statistics = variance exzplianed by the model/variance not explained by the model = effect/error

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Correlation Coefficient "r"

A statistic used to describe the linear relationship between two variables

Provides information about DIRECTION and MAGNITUDE OF THE RELATIONSHIP

Can be positive or negative.

Range from -1 to 1

correlation 0 means no relationship

Effect size is not influenced by sample size.

1. They describe the strength of an effect on a

continuous scale, with 0 representing “no

relationship”.

2. They come with standard conventions for what

values constitute small, medium, and large effects.

3. They provide an index of the “practical significance”

of research findings.

4. They are used to compare the results of two or

more studies (meta-analysis).

5. They are used in “power analyses” to determine

how many subjects are needed in a study.

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