psyc 218 mid-term 1
Card Set Information
psyc 218 mid-term 1
a population is the complete set of individuals, objects, or scores that the investigator is interested in studying.
a sample is a subset of the population
a variable is any property or characteristic of some event, object, or person that may have different values at different times depending on the conditions
Independent variable (IV)
the IV in an experiment is the variable that is systematically manipulated by the investigator
Dependent Variable (DV)
the DV in an experiment is the variable that the investigator measures to determine the effect of the independent variable
the measurements that are made on the subjects of an experiment are called data
a statistic is a number calculated on sample data that quantifies a characteristic of the sample
a parameter is a number calculated on population data that quantifies a characteristc of the population
is concerned with techniques that are used to describe or characterize the obtained data
involves techniques that are used the obtained sample data to infer to populations
no variables are actively manipulated--> can't say anything about causality; includes 1) naturalistic observation, 2) parameter estimation, 3) correlation
causality is assigned--> manipulate one variable, compare to un-manipulated situation--> is there an effect?
equal probability of being selected for the study
lowest level of measurement; often used with variables that are qualitative in nature; e.g. types of jogging shoes, gender, nationality, etc
possess a relatively low level of property of “magnitude”; objects that are being measured are “rank ordered”; e.g. order an individual places in a race-first, second third
possesses the properties of magnitude and an equal interval between adjacent units; no absolute zero point; e.g., Celsius scale
same properties as Interval scale, but possesses a true zero point; e.g., reaction time, weight, age, etc.
Acronym for measurement Scales?
can theoretically have an infinite number of values between adjacent units on the scale.
there are no possible values between adjacent units on the scale.
Real limits of a variable:
those values that are above and below the recorded value by one half of the smallest measuring unit of the scale.
A frequency distribution...
presents the score values and their frequency of occurrence
a relative frequency distribution...
indicates the proportion of the total number of scores that occurs in each interval
A cumulative frequency distribution...
indicates the number of scores that fall below the upper real limit of each interval
cumulative percentage distribution ...
indicates the percentage of scores that fall below the upper real limit of each interval
a percentile of percentile point...
is the value on the measurement scale below which a specified percentage of scores in the distribution fall
the percentile rank...
of a score is the percentage of scores with values lower then the score in question
a curve is symmetrical ...
if when folded in half the two sides coincide
if a curve is not symmetrical, it is...
when a curve is positively skewed,...
most of the scores occur at the lower values of the horizontal axis and the curve tails off toward the higher end.
when a curve is negatively skewed,...
most of the scores occur at the higher values of the horizontal axis and the curve tails off toward the lower end
When constructing a Frequency Disstribution of Grouped scores. What is the formula for Determining interval width (
The arithmetic mean is defined as...
the sum of the scores divided by the number of scores
mean of sample)
N = number of scores
(mean of population set of scores)
The median is ...
defined as the scale value below which 50% of the scores fall. It is therefore the same thing as
The mode is...
defined as the most frequent scores in the distribution. (when all scores in the distribution have the same frequency it is customary to say that the distribution has no mode)
The range is...
defined as the difference between the highest and lowest scores in the distribution
A deviation score...
tells how far away the raw score is from the mean of its distribution
in equation form, what is a deviation score for sample data and for population data?
in equation form, what is the standard deviation score of a sample by the raw scores method?
A z-score is...
a transformed score that designates how many standard deviation units the corresponding raw score is above or below the mean
for population and sample
A scatter plot is...
a graph of paired X and Y values
A linear relationship between two variables is...
one in which the relationship can be most accurately represented by a straight line.
the slope of a line
Regression is ...
a topic that considers using the relationship between two or more variables for prediction
A regression line is...
a best fitting line used for prediction
A perfect relationship is...
one in which a positive or negative relationship exists and all of the points fall on the line.
An imperfect relationship is...
one in which a relationship exits, but all of the points do not fall on the line.
A correlation coefficient...
expresses quantitatively the magnitude and direction of the relationship.
is a measure of...
the extent to which paired scores occupy the same or opposite positions within their own distributions.
The least-squares regression line is...
the prediction line that minimizes the total error of prediction, according to the least-squares criterion of
Spearman rho is ...
used for linear relationships when one or both of the variables are only of ordinal scaling
the equation for the least-squares regression line for predicting Y given X is ...
predicted or estimated value of Y
slope of the line for minimizing errors in predicting Y
= Y axis intercept for minimizing errors in predicting Y
regression constant is equal to...
regression constant is given by...