# Statistics Vocabulary

## 90 terms

### categorical variables

another name for qualitative variables (are not numeric variables)

### qualitative variables

non-numeric data (e.g. color)

### quantitative variables

numeric variables (they can be continuous variables)

used for mutually exclusive random events. the chance of at least one of them occuring is the sum of their individual probablities.

### alternative hypothessi

a research hypothesis; the hypothesis that is supported if the null hypothesis is rejected

### bar chart

a graphic that displays how data falls into different categories or groups

### bias

the consistent underestimation or oversestimation of a true value, because of preconceived notion of the person sampling the population

### gaussian curve

bell-shaped/normal curve

### bimodal

curve with two equal scores of highest frequency

### binomial

event with only two possible outcomes

### binomial probablitiy distribution

for binomial events, the frequency of the number of favorable outcomes. For a large number of trails, the binomial distribution approaches the normal distribution

### bivariate

involving two varibales, especially, when attempting to show a correlation between two variables.

### box plot

a graphic display of data indicating symmetry and central tendency

### Central Limit Theorem

a rule that states that the sampling distrubution of means from any population will be normal for large sample "n"

### chi-square

a probability distribution used to test the independence of two nonimal variables

### class frequency

the number of observations that fall into each class interval

### class intervals

categories or groups contained in frequency graphics

### coefficient of determination

a measure of the proportion of each other's variablility that two variables share

### confidence interval

the range of values that a population parameter could take at a given level of significance

### confidence level

the probablity of obtaining a given result by chance

### continuous cariable

a variable that can be measured with whole numbers and fractional (or decimal) parts thereof

### correlated

two(or more) quantities that change together in a consistent manner. Thus, if the value of one variable is known, the other can be immediately determined from their relationship

### correlation coefficient

a measure of the degree to which two variables are linearly related

### critical value

the value of a conmputed statistic used as a threshold to decide whether the null hypothesis will be rejected.

### degrees of freedom

a parameter used to help select the critical value in some probablility distribution

### dependent events

events such that the outcome of one has an effect on the probablity of the outcome of the other

### dependent varibale

a variable that is caused or influenced by another

### descriptive statistics

numberical data that describe phenomena

### divation

the distance of a value in a population or sample from the mean value of the population or sample

### directional test

a test opf the prediction that one value is higher than another'; also called a one-tailed test

### discrete variable

a variable that can be measured only by means of whole numbers; or one which assumes only a certain set of definite values, and no others

### disjoint occurrence

both outcomes unable to happen at the same time

### distribution

a collection of meansurements; how scores tend to be dispersed about a measurement scale

### dot plot

a graphic that displays the variablity in a small set of measures

### doublt counting

a mistake encountered in calculating the probablility of at least one of several events occuring, when the events are not mutually exclusive. In this case, the addition rule does not apply

### emprical rule

a rule that is dounded on observation, without a theoretical basis. Or a "rule of thumb"

### frequency distribution

the frequency of occurence of the values of a variable. For each possible value of the variable, there is ana ssociated frequency with which the variable assumes that value

### frequency histogram

a graphic that displays how many measures fall into different classes, giving the frequency at which each category is seen observed

### frequency polygon

a graphic presentation of frequency of a phenomenon that typically uses straight lines and points

### grouped data

data that has eben sorted into categories, usually in order to construct a frequency histogram

### grouped measures

a set of values that belong to the same class

### histogram

a graphic presentation of frequency of a phenomenon

### independent events

events such that the outcome of one has no effect on the prbabality of the outcome of the other

### independent variable

a variable that causes, or influences, another variable

### inference

conclusion about a population parameter bases upon analysis of a sample statistic. Inferences are always stated with a confidence leve

### intercept

the value of "y" at whcih a line crosses the vertical axis

### interquartile range

set of measures lying between the lower quartile (25th percentile) and the upper quartile (75th percentile), inclusive.

### interval

a scale using numbers to rank order; its intervals are equal but with an arbitrary zero point

### joint occurance

both outcomes happening simultaneously; P(AB)

### least squares

any line-fitting or curve-fitting model that minimizes the squared distance of data points to the line

### lower quartile

(Q1) the 25th percentile of a set of measures

### mean

the sum of the measures in a distribution divided by the number of measures; the average

### measures of cnetral tendency

descriptive measures that indivate the center of a set of values, for eample, mean median, and mode

### measures of variation

descriptive measures that indicate the dispersion of a set of values, for example, variance, standard deviation, and standard error of the mean

### median

the middle measure in an ordered distribution

### middle quartile

(Q2) the 50th percentile of a set of measures; the median

### mode

most frequent measure in a distribution; the high point on a frequency distribution

### multiplication rule

the probability of two or more independent events all occuring is the product of their individual probabilities

### mutually exclusive

events such that the occurence of one precludes the occurence of the other

### negative relationship

a relationship between two variables such that when one increases, the other decreases

### negatively skewed curve

a probabalility or frequency distribution that is not normal, but rather is shifted such that the mean is less than the mode.

### nomial

a scale using numebrs, symbols, or names to desginate different subclasses

### non-directional test

a test of the prediction that two values are equal or a test that they are not equal;a two-tailed test

### non-parametric test

statistical test used when assumptions about normal distrubution in the population cannot be met, or when the level of measurement is ordinal or less. For example the z-square test

### normal distrubution

smooth bell-shaped curve symmetrical about the mean such that its shape and area obey the empirical rule

### null hypothesis

the reverse of the research hypothesis. It is directly tested by statistical analysis so that it is either rejected or not rejected, with a confidence level. If it is rejected, the alternative hyposthesis is supported

### numerical statistics

statistical parameters presented as numbers (as opposed to pictorial statistics)

### ogive

a graph that displays a running total

### one-tailed test

a test of the prediction that one value is higher than another

### ordinal

a scale using numbers or symbols to rank order; its intervals are unspecified

### outlier

a data point that falls far from most other points; a score extremely divergent from the other measures of a set

### parameter

a charateristic of a population. The goal of statistical analysis is usually to estimate population parameters, using statistics from a sample of the population

### Pearson's product moment coefficient

indentical to the correlation coefficient

### percentile

the calue in an ordered set of measurements such that P% of the measures lie below that value

### pictorial statistics

statistical parameters that are presented as graphs or charts (as opposed to simply as numbers)

### pie chart

a graphic that displays parts of the whole, in the form of a cirle with its area divided appropriately

### point estimate

a number computed froma sample to represent a population parameter

### population

a group of phenomena that have something in common. the population is the larger group, whose properties (parameters) are estimated by taking a smaller sample from within the population, and applying statistical analysis tot he sample

### positive relationship

a relationship between two variables such that when one increases, the other increases, or when one decreases, the other decreases

### positively skewed curve

a probability of frequency distribution that is not normal, but rather is shifted such taht the mean is freater than the mode.

### power

the probability that a test will reject the null hypothesis when it is, in fact, false.

### probability

a quantitative measure of the chances for a particular outcome or outcomes

### probability distribution

a smooth curve indicating the frequency distribution for a continuous random variable

### proportion

for a binomial random even, the probability of a successful (or favorable) outcome in a single trial.

### qualitative variable

phenomenon measured in kind, that is, non-numberical units. For example, because it cannot be expressed simply as a number

### quantitative variable

phenomenon measured in amounts, that is, numerical units. For eample, length is a quanitative variable.

### random

an event for which there is no way to know, before it occurs, what the outcome will be. Instead, only the probabilities of each possible outcome can be stated.

### random error

error that occurs as a result of sampling variability, through no direct fault of the sampler. It is a reflection of the fact that the sampler. It is a reflection fot ehf act that the sample is smaller than the population; for larger smaples, the random error is smaller

### range

difference between the largest and smallest measures of a set

### ratio

a scale using numbers to rank order; its intervals are equal, and the scale has