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