Experimental Psychology

Statistics

a science of collecting, organizing, summarizing, analyzing, and interpreting data in order to make decisions or provide answers or solutions to an inquiry

• Characterize persons, objects, situations, and phenomena

• Explain relationships among variables

• Formulate objective assessments and comparisons

• Make evidence-based decisions

  and predictions

Statistics enables us to

Descriptive Statistics

branch of statistics that involves the organization, summarization, and display of data (graphs, perecentages, numbers)

Inferential Statistics

branch of statistics that involves using a sample to draw conclusions or make predictions about a population (estimations, relationships)

Variable

characteristics or attribute that can assume different values

Data

values (measurements or observations) that the variables can assume

Data set

a collection of data values

Data value

a value specific to a particular variable in a data set

Qualitative Variables

express a categorical attribute

Quantitative Variables

can be counted or measured

Discrete Variables

variables that can take on a finite number of values, often counted as whole numbers and cannot be subdivided

Continuous Variables

variables that can take on an infinite number of values within a given range, often measured (fractions, decimals)

Nominal

variables that represent categories or groups without a specific order, (gender or ethnicity)

Ordinal

variables that represent categories with a specific order or ranking, (education level or socioeconomic status)

Interval

variables that have both order and equal intervals between values but no true zero point, (temperature in Celsius or Fahrenheit)

Ratio

variables that have both order, equal intervals between values, and a true zero point, (height or weight)

• Published Sources

• Experiments

• Surveys

Methods of Data Collection

Population

collection of all outcomes, responses, measurements or counts that are of interest, (Census)

Sample

a subset, or part of a population, (Survey)

Parameter

a numerical description of a population

Statistic

a numerical description of a sample used to estimate a population parameter.

Random Sampling

sample in which all members of the population have an equal chance of being selected

Systematic Sampling

sample obtained by selecting every k^th member of the population where k is a counting number

Stratified Sampling

sample obtained by dividing the population into subgroups or strata and randomly selecting members from each subgroup

Cluster Sampling

sample obtained by dividing the population into sections or clusters and randomly selecting entire clusters rather than individuals

Convenience Sampling

sample obtained by selecting respondents who are convenient to the researcher

Volunteer or Self-selected Sampling

sample obtained by letting people decided for themselves if they wish to participate

Sampling Error

difference between results obtained from a sample and the results obtained from the population from which the sample was selected

Non-probability Sampling Techniques

Purposive Sampling and Snowball Sampling

Bar Graph

visualizes a categorical variable as series of bars, where the length of each bar is proportional to the value it represents

Histogram

visualizes as a vertical bar, where each bar represents a class interval from a frequency or percentage distribution (bars have no gaps)

Descriptive Statistics

A survey of 2, 234 people conducted by the Harris Poll found that 55% of the respondents said that excessive complaining by adults was the most annoying social media habit

Inferential Statistics

Last August 31, 2021, the OCTA Research Group predicted that the average daily cases of COVID for the first week of Sep 2021 would be 25, 000

Quantitative

Amount of time it takes to assemble a simple puzzle

Quantitative

number of errors in a midterm exam

Qualitative

rating of a newly elected politician (excellent, good, fair, poor

Qualitative

region in which a person lives

Discrete

each of several physicians plants to count the number of physical examinations given during the next full week

Continuous

when the typical patient has blood drawn as part of a routine examination, the volume of blood drawn is between 0 mL and 50 mL

Continuous

exact length of feet from a sample

Discrete

number of times spent texting while driving

Interval

temperature

Ration

weight

Nominal

zip code

Ordinal

grade level

Population

all small business owners

Sample

614 small business owners

Data Set

258 owners said yes, 365 said no

Cluster Sampling

out of 10 hospitals in a municipality, a researcher selects one and collects records for a 24-hour period on the types of emergencies that were treated there

Stratified Sampling

researcher divides a group of students according to gender, major field, and low, average and high grade point average. then randomly selects six students from each group

Random Sampling

the subscribers to a magazine are numbered, then a sample of these people is selected using random numbers

Systematic Sampling

Every 10th bottle of Super-Duper Cola is selected, and the amount of liquid is measured to assess the consistency of the product's fill level