STA 2023 Ch. 1-3 Study Guide

Class Width

Calculated by subtracting upper and lower class boundaries. It is the amount of whole numbers in a class. For example, if a class is 1-9, and 10-18, the class width would be 9.

Nominal

Categorical (names). Ex: hair color, zip codes.

Qualitative Data

Categorical data. Information about qualities; information that can't actually be measured.

Example of Descriptive Statistics

In 2011, there were 34 deaths from the avian flu.

Experimental Study

Research manipulates independent (explanatory) variable, and tries to determine how the manipulation influences dependent (outcome) variable.

Class Boundaries

Separate classes. Can be found averaging the upper class limit of one class, and the lower class limit of the next class. For example, if a class is 100-104, the class boundaries would be 99.5-104.5

Upper and Lower Class Limits

Smallest and largest possible data values in a class. For example, if a class was 100-104, the upper class limit would be 104, and the lower class limit would be 100.

Sample

Subset of population.

Example of Quantitative Data

The age of your car. The number of hairs on your knuckle. The number of pennies in your pocket. The weight of the backpacks on first graders on a school bus.

Shape of Distribution in Graphs

Bell shape, uniform, J-shaped, reverse J-shaped, right skewed, left skewed, bimodal, and U-shaped.

Example of Inferential Statistics

80% of all people living in Italy have the last name Nicolussi.

Convenient Technique

A bad form of sampling such as mall surveys.

Rules for Classes in Group Frequency Distribution

1) Should be 5-20 classes. 2) Class width should be an odd number. 3) Classes must be mutually exclusive (can't overlap). 4) Must be continuous (1-9, 10-18). 5) Must be exhaustive (includes all data gathered). 6) Must be equal width (except in open-ended distributions).

Example of Continuous Data

2.59, 31.21, 459.007, etc. Cubic feet of insulation in an attic.

Example of Discrete Data

5, 29, 57, etc. Red or blue, male or female, etc. Number of breeds of dogs at a dog show.

Variable

A characteristic or attribute that can assume different values.

Grouped Frequency Distribution

A distribution form used when the data range is large.

Discrete Data

A form of quantitative data that is countable or categorical. There may potentially be an infinite number of those values, but each is distinct and there's no grey area in between.

Continuous Data

A form of quantitative data that is not restricted to defined separate values, but can occupy any value over a continuous range. Between any two continuous data values there may be an infinite number of others. This data is also always numeric.

Random Technique

A form of sampling in which a random number generator randomly picks for sample.

Systematic Technique

A form of sampling in which every Kth subject is used. For example, every 5th is used in sample; so in a group of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, only 5 and 10 would be used.

Stratified Technique

A form of sampling in which the population is divided into "layers." For example, a population is divided into men and women, then an equal amount is taken from both.

Cluster Technique

A form of sampling that uses intact groups. For example, taking a random sampling from each Florida county.

Histogram

A graph that displays data by using vertical bars of various heights to represent frequencies, with class boundaries on the x (horizontal) axis and frequencies on the y (vertical) axis.

Ogive (Cumulative Frequency Polygon)

A graph that represents cumulative frequencies. The upper class boundaries on the x (horizontal) axis, and the cumulative frequency on the y (vertical) axis.

Frequency Polygon

A graph that uses lines to connect midpoints and has anchors on each end. Class boundaries on the x (horizontal) axis and frequencies on the y (vertical) axis.

Relative Frequency Graphs

A graph where proportions are used instead of frequencies. Used when proportions are more important.

Observational Study

A study in which the research observes and draws conclusions from observations without interfering.

Ratio

All other forms of measurement, except that there is a true zero present (no negative numbers), and the ratios are consistent. Ex: height, age.

Population

Consists of all subjects (human or otherwise) that are studied.

Descriptive Statistics

Consists of collection, organization, summarizing, and presentation of data.

Inferential Statistics

Consists of generalizing from samples to population, estimating, hypothesis test, determining relationships among variables, and making predictions.

Raw Data

Data collected in original form.

Confounding Variable

Influences dependent variable, but cannot be separated from independent variable. An example would be climate

Ordinal

Nominal, but data can be ranked in a meaningful order. Ex: Letter grades.

What are the four levels of measurement from lowest to highest?

Nominal, ordinal, interval, and ratio.

Categorical Frequency Distribution

Nominal/ordinal level data that can be organized and put into categories.

Quantitative Data

Numerical, can be ranked. Information about groups; that is, information that can be measured and written down with numbers.

Interval

Ordinal, but the intervals are consistent, and there is no real zero. Ex: ACT score, temperature.

Frequency Distribution

Organization of raw data in table form, using classes and frequencies. Table is a frequency distribution.

What are the two types of data?

Qualitative and Quantitative.

Class Midpoint Xm

The midpoint of a class. Can be calculated by averaging upper and lower class limits/boundaries. For example, the midpoint of a class that's 115-119 is 117.

Statistics

The science of conducting studies to collect, organize, summarize, analyze, and draw conclusions from data.

Example of Qualitative Data

The softness of a cat. The color of the sky.

Data

The values that a variable can assume.