Statistics

strong coorelation

how much there is a clear pattern of some particular relationship between two variables. the closer to 1 or -1 correlation equals the stronger the coorelation.

discrete variable

number of time you want to the dentist last month, , gender, religious affiliation

Prediction variable

variable used to predict score o other variable

median

is the middle score in a data set, it is used as a measure f central tendency when extreme outlier can affect the validity of the mean,

regression line

line on a graph such as a scatter diagram showing the predicted value of the critetion variable for each value of the predictor variable; visual display of the linear prediction rule

theory

a general principle or set of principles about a class of events Used to:Explain a phenomena, Predict new information, Allow scientists to use logical deductive reasoning to formulate testable hypotheses

scatter diagrams/ scatter plot

a graph showing the relationship between two variables the values of one variable are on the horizontal while the variables of another are on the vertical axis

Large correlation

a large correlation in psychology is considered to be about .5 or above a moderate coorelation canbe about .3 and small coorelation about .1

score

a particular persons value on an variable

correlation

a relationship between scores on two variable. a correlation is significant when the P value is less that .05, its marginally significant if p values is between .o1 & ,051, P values > .1 are NOT significant. a summary of the matchness of z scores,

Raw score

am ordinary score (or any number ina distribution before it has been made a z score.

scientific method

an experimental technique used to answer questions

Unreliability of measure attenuation

many factors can affect the validity of measurement in an experiment. IE certain life events , external circumstances that cannot e controlled, natural disasters can change the way a person scores. creating an attenuation in the correlation

Sample statisics

mean and standard deviation known from a sample, use Roman letters.

Variance

measures of how spread out a set of scores are : average of the squared deviation from the mean the more spread out a distribution is the larger the variance, the less spread out it is the smaller the variance

Linear prediction rule

formula for making predictions formula or predicting a persons score on a criterion variable based on the persons score on one or more of the predictor variable

normal curves/distribution

frequency distribution that follows a normal curve. specific, bell-shaped frequency distribution that is symmetrical and uni modal; distributions observed in nature and in research commonly approximate it

Random sampling

method of selecting a sample that uses truly random procedure(usually meaning hat each person in the population and select a group of them to study using a table of random numbers

zero correlation

no systematic relation between two variables, coorelation = 0

rank order variable

numeric variable in which the values are ranks such as class standing, or place finised in a race

reporting correlations

i.e. there was a positive correlating (r = .51) between excitement of activivties done wit partner ad marital status r = .51, p < .05

levels of measurement/Kinds of variables

numeric, equal interval ratio scale rank order variable nominal variable types of underlying information provided by a measure such as equal- interval, rank order, and nominal category.

prediction in reasearch

prediction is not commonly used in research articles. however this is usually done when there is more than one group and researchers want to illustrate the difference in the linear prediction between the two groups.

Descriptive statistics

psychologists use descriptive statistics to summarize and describe a group of numbers from a research study

Inferential Statistics

psychologists use____ to draw conclusions and to make inferences that are based on the numbers from a research study but that go beyond the numbers.

Inductive reasoning

reasoning fro specific to general "bottom up" 100% of biological life forms that we know of depend on liquid water to exist. Therefore, if we discover a new biological life form it will probably depend on liquid water to exist.

Deductive reasoning

reasoning from general to specific "top down". All men are mortal. Socrates is a man. Therefore, Socrates is mortal.

negative correlation

relation between two variables in which high score in one goes with low score on the other. medium with medium and low with high. the dots follow a straight line sloping downward

positive coorelation

relation between two variables in which high scores on one go with high score on the other, the dots form a line sloping upward.

Error

the the difference between the predicted score and the actual score in the criterion variable

independent variable

the variable you have control over, and chooses to manipulate. You are interested in how stress affects heart rate in humans. Your independent variable would be the stress and the dependent variable would be the heart rate. You can directly manipulate stress levels in your human subjects and measure how those stress levels change heart rate.

scientific method functions

theory, formulate hypothesis using deductive reasoning, conduct study, analyze and interpret results using inductive reasoning.

population parameters

usually is unknown and can only be estimated from a sample, usually shown in Greek letters

continuous variable

value for which in theory there are infinite number of values between any two values.

mode

value with the greatest frequency on a distributuon used to describe central tendency for a nominal value

equal interval variable

variable in which the numbers stands for approximate equal amounts. for example GPA , Scales from 0 to 10 ,

criterion varaible

variable predicted x given y Y criterion X predictor

NUmeric variable

variable whose values are number as opposed to names, also called quantitative variable.

nominal variable

variable with values that are gategories, namesrather than numbers

Causality

what is causing what, if X is thought to cause Y then the direction of casualty is X to Y possible directions of casulaity ARE X to y Y to X or some external variable causing X and Y

dependent variable

what you measured int the experiment and what is affected during he experiment, It is called dependent because it "depends" on the independent variable. In a scientific experiment, you cannot have a dependent variable without an independent variable. Example: You are interested in how stress affects heart rate in humans. Your independent variable would be the stress and the dependent variable would be the heart rate. You can directly manipulate stress levels in your human subjects and measure how those stress levels change heart rate.

value

Number or category that a score can have

intercept

the point where the the regression line crosses the vertical axis

Attenuation

The reduction in a correlation due to the Unreliability of mearument

poulation

An entire group of people to wich a researcher intends the results to study to apply; larger group tp which inferences are made on the basis of the particular set of people(sample) studies

Two branches of statistical methods

Descriptive, and Inferential statistics.

Measures of dispersion

RANGE: how spread out are your scores D-Statistic: split the data into percentiles & knock off the upper & lower 10%. Then find the range. Semi-interquartile range: break the data into quartiles Average absolute deviation of every score from the mean

CORRELATION MATRIX

common way of reporting the correlation coefficients among several variable in a research article ; table in which the variables are named on the top and along the side and the correlations among them are all shown

Variable

condition or characteristics that can have different values. stress level, gender , religion

restrictions in range

situation in which you figure a correlation but only a limited range of the possible values on one of the variables is included i n the group studied when a correlation happens in only in limited range of the data set

ratio scale

some equal interval variable are measured in what is called a ratio scale . an equal interval variable is measured in a ratio scale if it has an absolute zero point. like # of siblings, or , distance, time and weight

Haphazard sampling

taking whoever just happens to be available or happens to be fist on a list

Variablitly

the amount of spread of the scores around the mean. how close or how far from the mean are the score in a distribution.

Variablilty

the amount of variation among the scores

standard deviation

the average amount the scores drifted from the mean square root of the average of the squared deviation from the mean; the most common descriptive statistic for variation.

mean

the best measure oc central tendency is the ordinary average,

Spearmans rho

the equivalent of a correlation for rank order scores

Mean and standard deviation of a Z score

the mean of a distribution of z scores is always 0 standard deviation is always 1

central tendency

the most representative value of a group of scores, the mean , media, mode

Z score

the number of standard deviations a score is above or below the mean, if the score is above the mean its positive if its below the ,mean its negative. it helps better describe the scores location and distribution.

sample

the particular group studies, considered to be representative of of the score in some large population