Chapter 6 Descriptive Research (Video Notes)

60 vocabulary flashcards covering key terms from Chapter 6: Descriptive Research as presented in the video notes.

Descriptive research

Research aimed at describing the characteristics or behaviors of a population in a systematic, accurate way.

Survey research

The most common type of descriptive research; uses questionnaires, interviews, or observation to describe attitudes, beliefs, feelings, or behaviors.

Questionnaire

A set of written questions used to collect data from participants.

Cross-sectional survey design

A survey design in which a single group of respondents is surveyed at one point in time.

Successive independent samples design

Two or more samples answer the same questions at different times; samples are different people but selected in the same way.

Longitudinal (panel) survey design

A single group of respondents is questioned more than once; follow-up may suffer from dropout.

Internet surveys

Surveys conducted online (e-surveys); inexpensive and convenient but with sample control and verification challenges.

Demographic research

Describes patterns of basic life events (birth, marriage, divorce, migration, death) and related predictors.

Epidemiological research

Study of the occurrence of disease and death in groups; used to identify at-risk groups and describe prevalence and incidence.

Prevalence

The proportion of a population that has a particular disease or condition at a given time.

Incidence

The rate at which new cases of a disease or condition occur over a specified period.

Frequency distribution

A table that shows how many scores fall into each category.

Simple frequency distribution

A frequency distribution that shows the number of participants for each exact score.

Grouped frequency distribution

A frequency distribution that uses class intervals to group scores.

Class interval

A range of scores used in a grouped distribution.

Mutually exclusive

Class intervals are mutually exclusive; a score fits in only one interval.

Equal class intervals

All class intervals have the same size.

Relative frequency

The proportion or percentage of the total that falls in each class interval.

Histogram

A graph with bars touching each other to display a frequency distribution for interval/ratio data.

Bar graph

A graph with separated bars used for nominal or ordinal data; bars do not touch.

Frequency polygon

A graph formed by connecting the frequencies of class intervals with a line.

Normal distribution

A bell-shaped distribution in which scores cluster around the mean.

Bell-shaped distribution

Another term for a normal distribution indicating a symmetrical, bell curve.

Skewed distribution

A distribution that is asymmetrical, with tails longer on one side.

Positively skewed

A skew where the tail is on the right; more low scores with a long right tail.

Negatively skewed

A skew where the tail is on the left; more high scores with a long left tail.

Range

The difference between the largest and smallest scores.

Variance

The average of the squared deviations from the mean; a measure of variability in squared units.

Standard deviation

The square root of the variance; a variability measure in the original units.

Confidence interval

A range around a sample statistic within which the population parameter is expected to fall.

95% confidence interval

The interval that would contain the true population mean in 95% of repeated samples.

Error bars

Vertical lines on a graph indicating the uncertainty around a mean (often a confidence interval).

Sampling error

Error arising from observing a sample instead of the entire population.

Mean

The arithmetic average of a set of scores.

Median

The middle score when data are ordered; the value that splits the distribution into halves.

Mode

The most frequently occurring score in a distribution.

Outlier

A score that is unusually far from the rest of the data; extreme value.

Raw data

The original measurements before processing or summarization.

Measures of central tendency

Statistics that describe the center of a distribution (mean, median, mode).

Measures of variability

Statistics that describe the spread of a distribution (range, variance, standard deviation).

Population

The entire group of individuals of interest in a study.

Sample

A subset of the population used to infer about the population.

Grouped distribution characteristics

Three features: mutually exclusive class intervals, cover all scores, and equal interval size.

Covariance

A measure of how two variables vary together; direction indicates positive or negative relation.

Correlation coefficient (r)

A standardized index of the strength and direction of the linear relationship between two variables.

Coefficient of determination (R^2)

The proportion of variance in one variable explained by the other in a correlation.

Numerical method

Describing data with numbers (percentages, means, etc.) rather than graphs.

Graphical method

Presenting data with graphs (histograms, bar charts, etc.).

Cross-sectional vs longitudinal differences

Cross-sectional surveys sample one time; longitudinal tracks the same individuals over time to observe changes.

Comparable samples

In successive independent samples designs, samples must be drawn in the same way so they are comparable.

Margin of error

An estimate of the range around a sample statistic within which the population parameter lies.

Gee-whiz graph

A graph designed to attract attention but potentially misleading about data.

Confidence interval interpretation

A description of what a CI tells us about the precision of a mean estimate.

I-shaped error bars

Error bars shaped like the letter I, indicating the 95% CI around means in a bar graph.

Interview

A data collection method where a researcher asks questions directly to a participant.

Accuracy

Correctness of data descriptions; one of the three criteria for good descriptions.

Conciseness

Brevity and clarity in presenting data; one of the three criteria for good descriptions.

Understandability

presentations should be easy to interpret; one of the three criteria for good descriptions.

Empirical rule

In a normal distribution, about 68% lie within ±1 SD, about 95% within ±2 SD, and about 99.7% within ±3 SD.

Z-score interpretation

A z-score shows how far a score is from the mean in units of standard deviation.