Stats

One goal of research is to learn the causes of variability.

By researching the variable, we hope to learn to grow plants that yield the best tomatoes. That is, why do some tomatoes weigh more than others?

A continuous variable is a quantitative variable that has an infinite number of possible values that are not countable. A continuous variable may take on every possible value between any two values.

Continuous variables typically result from measurement. Continuous variables are often rounded. If a certain make of car gets 24 miles per gallon (mpg) of gasoline, its miles per gallon must be greater than or equal to 23.5 and less than 24.5, or 23.5≤mpg<24.5.

If variables did not vary, then they would be constants and inferential statistics would not be necessary.

If each tomato had the same weight, then knowing the weight of one tomato would be enough information to determine the weights of all tomatoes.

Variables vary, meaning that a variable can take on different values.

My son noted that the tomatoes had different weights even though they came from the same plant. He discovered that a variable (weight) varies.

Variables that are nominal or ordinal are _____________ variables. Variables that are interval or ratio are ____________ variables.

Qualitative, Quantitative

The characteristics of the individuals in a study are variables.

Recently, my son and I planted a tomato plant in our backyard. We were interested in studying the weights (the variable) of each tomato (the individuals).

A discrete variable is a quantitative variable that has either a finite number of possible values or a countable number of possible values. A discrete variable cannot take on every possible value between any two possible values.

The term countable means that the values result from counting, such as 0,1,2,3, and so on.

Variables can be classified into two groups: qualitative and quantitative. Qualitative, or categorical, variables allow for classification of individuals based on some attribute or characteristic. Quantitative variables provide numerical measures of individuals. The values of a quantitative variable can be added or subtracted and provide meaningful results.

Variables can be classified into two groups: qualitative and quantitative. Qualitative, or categorical, variables allow for classification of individuals based on some attribute or characteristic. Quantitative variables provide numerical measures of individuals. The values of a quantitative variable can be added or subtracted and provide meaningful results.

Ratio Level of Measurement

has the properties of the interval level of measurement and the ratios of the values of the variable have meaning. A value of zero means the absence of the quantity. Arithmetic operations such as multiplication and division can be performed on the values of the variable.

Ordinal Level of Measurement

has the properties of the nominal level of measurement. However, the naming scheme allows for the values of the variable to be arranged in a ranked or specific order.

Interval Level of Measurement

has the properties of the ordinal level of measurement and the differences in the values of the variable have meaning. A value of zero does not mean the absence of the quantity. Arithmetic operations such as addition and subtraction can be performed on the values of the variable.

Nominal Level of Measurement

the values of the variable name, label, or categorize. In addition, the naming scheme does not allow for the values of the variable to be arranged in a ranked or specific order.