Psychology 202 Chapter 2 Exam 1

Frequency Table

a tool used in statistics to organize and show how often each value or category occurs in a data set. It is the specific chart or grid used to display data

Frequency distribution

a tool that organizes raw data into a table or graph to show how often each value or group of values occurs

Probability Distribution

a list or a map that shows all the possible outcomes of an event and how likely each outcome is to happen

Discrete Variable

a variable that can take on a finite number of values, often counted in whole numbers, such as the number of children in a family.

• a piece of data that can only take specific, separate values and cannot be divided into decimals or fraction

• Can be nominal or ordinal

Continuous Variables

a number that can take any value within a range, including decimals and fractions

• Infinite numbers of possible values

• Can be interval or ratio

Grouped frequency distribution

a way to organize a large list of numbers into small, easy-to-read intervals or groups, showing how often values fall into each group

Historgram

a type of graph that uses connected vertical bars to show how often numerical data values fall within specific ranges

Probability density

a list or a graph that shows all the possible outcomes of an event and how likely each outcome is to happen

Normal distribution

a data pattern shaped like a symmetric bell curve, where most values cluster around a central average and taper off equally on both sides

Positive skewed

a distribution where most values are concentrated on the left side, with a long tail extending to the right.

Negative Skew

a distribution where most values are concentrated on the right side, with a long tail extending to the left.

Bimodal distribution

a probability distribution or data set with two distinct peaks (modes) where data values cluster most frequently

Leptokurtic

is a distribution that has a higher peak than a normal distribution, indicating a greater concentration of values near the mean and heavier tails.

Platykurtic

is a distribution that has a lower peak than a normal distribution, indicating a flatter shape with lighter tails and a broader spread of values.

Statistics

a set of mathematical procedures for organizing, summarizing, & interpreting info

• Explores why one group is the same or different than another

Variable

Any characteristic or condition that can take on different values

• Letter grades such as A, B, C, and D have different percentages or scores within a specific range and can change based on student performance.

Data

Measurements or observations obtained in a research study

Population

The complete set of all individuals of interest in a study

Sample

A subset of the population

Calculate Mean Formula

ΣX/N

• ΣX: Sum of all values in the dataset

• N: The total number of values in the dataset

• Mean: Remove below or add above (increase)

• Remove above or add below (decrease)

• Same as mean = no change

Calculate the Median

1. Write them in ascending order

2. Cross of min and max

3. Repeat until 1 or 2 numbers are left

4. If 1 that is median if 2 take an average and that’s is median

• removing any number changes median

  • 1, 2, 4, 6, 8, 10 = removing ANY number changes median

  • 1, 2, 4, 4, 6, 6 removing 6 or 4 = no change

How to calculate Mode

Most frequently occurring score

• Not affected unless score(s) removed as mode

  • That is only true when a few scores create mode

Outliers

• Some measures are highly impacted

  • Mean, range, and standard deviation (ss and Variance)

• Other measures are less sensitive

  • Median Mode, IQR (inter-quartile range)

How to calculate Variability

• SS (Sum of squared deviations): Σ(X-M)²

  • Inside () is the deviation

• Variance: SS/n-1(N)

  • Mean squared deviation

• Standard deviation: sqrt/variance

  • Mean devation

• Range: Max minus Min

  • IQR: 75% - 25%

How is Variability influenced by adding or removing a score

• IQR (inter-quartile range)

  • Change depends on whether score is above or below median

  • Added above or removed below = shift up

  • Remove above or add below = shift down

• Standard deviation (variance & SS)

  • Add above or removed below = Increase

  • Add below or remove above = decrease

• Range: Not Affected unless…

  • Add: Affected if number is above Max or below Min

  • Remove: Affected if number is Max or Min