Statistics Exam 1

Descriptive statistics

Summarize and describe a group of numbers from a research study

Inferential statistics

Draw conclusions/make inferences that are based on the numbers from a research study but go beyond the numbers

Variable

conditions or characteristic that can have different values

Value

number or category

Score

A particular person’s value on a variable

Equal-interval

Numeric value in which differences between values correspond to differences in the things being measured

Ratio-scale

an equal-interval variable is measured on a ratio scale if it has an absolute 0 point

Rank-order

Numeric value in which values correspond to the relative position of things measured

Nomial

Variable in which the values are categories

Discrete variables

variable that has specific values and that cannot have values between these specific values

Continuous variables

variable for there are an infinite number of values between any two variables

Interval

range of values in a grouped frequency table that are grouped together

Histogram

barlike graph of a frequency distribution in which the values are plotted along the horizontal axis and the height of each bar is the frequency of the value

Unimodal distribution

frequency of distribution with one value clearly having a larger distribution than any other

Bimodal distribution

frequency distribution with approximately two equal frequencies, each clearly larger than the others

Multimodal distribution

frequency distribution with two or more high frequencies separated by a lower frequency

Rectangular distribution

frequency distribution in which all values have approximately the same frequency

Symmetrical distribution

the pattern of frequencies on the left and right side are mirror images of each other

Skewed distribution

distribution in which the scores pile up on one side of the middle and are spread out on the other side; distribution that is not symmetrical

Ceiling effect

score pile up at high end of distribution

Floor effect

scores pile up at the low end of a distribution

Normal curve

bell-shaped frequency distribution that is symmetrical and unimodal

kurtosis

extent to which a frequency distribution deviates from a normal curve

pseudoscience

uses methods, theories, assumptions, and conclusions that pretend to be scientific

the properties of an abstract number system are

identity, magnitude, equal intervals, true zero

identity

each number has a particular meaning

magnitude

numbers have an inherent order from smaller to larger

equal intervals

the difference between units is the same anywhere on the scale

true zero

a nonarbitrary point indicating a zero level or the variable being measured

nominal scales

lowest level of measurement; the do no match the number system well

ordinal scales

have the property of magnitude as well as identity

interval scales

have properties of ordinal scales, in addition to equal intervals between consecutive values

ratio scales

provide the highest level of measurement

central tendency

a typical or most representative value of a group of scores

mean

arithmetic average of a group of scores

mode

value with the greatest frequency in a distribution

median

middle score when all the scores in a distribution are arranged from lowest to highest

outlier

score with an extreme value in relation to the other scores in a distribution

variance

measure of how spread out a set of scores are

deviation score

score minus the mean

squared deviation score

square of the difference between a score and the mean

sum of squared deviations

total of each score’s squared difference from the mean

standard deviation

square root of the average of the squared deviations from the mean

computational formula

equation mathematically equivalent to the definitional formula

definitional formula

equation for a statistical procedure directly showing the meaning of the procedure

behavioral variable

any observable response of an organism

stimulus variables

factors that have actual or potentially effects on an organism’s response

organismic variables

any characteristics of a subject

observed organismic variables

characteristics we can directly observe (age)

response-inferred organismic variables

characteristics that we cannot observe (racial attitudes)

dependent variabl

participants response to the manipulation

independent variable

variable manipulated by the experiment

manipulated independent variable

experimenter actively controls

non-manipulated independent variables

researchers assign participants to groups based on preexisting characteristics

causal relationship

one variable results in a predictable change in the other

extraneous variable

unplanned and uncontrolled factors that can arise in a study and affet the outcome

control

the procedures used to reduce extraneous influences in research

ethical research with humans depends on what?

beneficence, autonomy, and justice

beneficence

risk minimized and the benefits should be maximized

autonomy

participants have a right to decide if they want to participate

justice

both risks and benefits of research should be shared equally by all members of the population

deception/concealment

involves deliberately misleading participants by giving false information or by withoulding some information

debriefing

involves explaining to the participants the true nature of the deception/concealment as soon as possible

informed consent

principle that participants have the right to know exactly what they are getting into before they agree to participate in a study

Institutional Review Board

Formal body that reviews research proposals to determine if they meet ethical guidelines

Diversity

refers to how well the research sample represents various ethnic, cultural, age, and gender groups

z-score

the number of standard deviations that a score is above or below the mean of its distribution

raw score

ordinary score before it has been manipulated

normal distribution

frequency distribution that follows a normal curve

normal curve

specific, mathematically defined, bell-shaped frequency distribution that is symmetrical and unimodal

population

entire group of people to which a researcher intents the results of the study to apply

sample

scores of the particular group of people studied

population parameter

actual value of the mean, st. dev… for the population

sample statistics

descriptive statistics such as the mean or standard deviation, figured from the scores in a group of people studied

probability

expected relative frequency of an outcome; the proportion of successful outcomes to all outcomes

outcome

term used in discussing probability for the result of an experiment

expected relative frequency

number of successful outcomes divided by the total number of total outcomes you would expect to get if you repeated an experiment a large number of times

long-run relative frequency interpretation of probability

understanding of probability as the proportion of a particular outcome that you would get if the experiment were repeated many times

subjective interpretation of probability

way of understanding probability as the degree of one’s certainty that a particular outcome will occur

hypothesis testing

procedure for deciding whether the outcome of a study supports a particular theory or practical innovation

hypothesis

prediction, often based on informal observation, previous research, or theory, that is tested in a research study

theory

set of principles that attempt to explain one or more facts, relationships, or events

research hypothesis

statement in hypothesis testing about the predicted relation between populations

null hypothesis

statement about a relation between populations that is the opposite of the research hypothesis (theres no difference)

comparison distribution

represents the population situation if the null hypothesis is true

cutoff sample score

point in hypothesis testing, on the comparison distribution at which, if reached or exceed by the sample score, you reject the null hypothesis

conventional levels of significance

p<0.05, p<0.01

statistically significant

conclusion that the results of a study would be unlikely if in fact the sample studied represents a population that is no different from the population in general

directional hypothesis

research hypothesis predicting a particular direction of difference between popoulations o

one-tailed test

hypothesis testing procedure for a directional hypothesis

nondirectional hypothesis

research hypothesis that does not predict a particular direction of difference between the population

two-tailed test

hypothesis testing procedure for a nondirectional hypothesis

concurrent validity

assessing a measure by its correlation with criterion that has already been measured or can be measured simultaneously

covergent validity

when different studies using different operational definitions produce similar findings

criterion

variable we are attempting to predict in a regression

criterion-related validity

measures that are established by correlations with known criterion measures

effective range

the range over which the dependent measure accurately reflects the level of the dependent variable

internal consistency reliability

index of homogeneity of the items of a measure

interrater reliability

consistency of ratings between separate raters

measurement error

any inaccuracy found in the measurement of the variable