PSY 10 Exam 1

What is a discrete variable?

measured in categories or whole units and are not measured along a continuum. Not measured in fractional units.

What does M stand for?

sample mean: summation of X/ n

What is a percentile point?

The value of a score on a measurement scale below which a specified percentage of scores in a distribution fall.

Stem and leaf display

A graphical display that lists each individual score in the distribution, where the common digits shared by the scores are listed to the left as a "stem" and any remaining digits for each score are listed to the right as "leaf". It is important ot arrange the leafs from smallest to largest.

Histogram

A graphical display used to summarize the frequency of continuous data that are distributed in numeric intervals.

What would N mean?

The population size, all individuals belonging to a group of interest

independent variable

The variable that is manipulated in an experiment. By manipulating this we create the different groups in a study

What is Variability?

a measure of the dispersion of scores in a distribution, ranges from 0 to positive infinity

What is a weighted mean?

The combined mean of two or more groups of scores in which the number of scores in each group is disproportionate or unequal

How to find a percentile rank?

1. Identify the interval within which a specified percentile point falls. 2. Identify the real range for the interval identified 3. Find the position of the percentile point within the interval 4. Identify the percentile point

How to locate quartiles?

1. Locate the median quartile (Q2) 2. Locate the median for the remaining scores below Q2 this will give you Q1. 3. Locate the median for the remaining above scores, this will give you Q3

How would you find the real range?

= (largest value - smallest value) + 1

Ogive

A dot and line graph used to summarize the cumulative percent of continuous data at the upper boundary of each interval. The cumulative percent ranges from 0% to 100%

Frequency polygon

A dot and line graph used to summarize the frequency of continuous data at the midpoint of each interval. The midpoint is represented by a dot and the dots are connected by lines

What if there is an odd number of scores in a distribution? (finding median)

Calculate the median by ordering the scores from least to greatest and counting in to the middle score. n+1/2 then count in by that many scores

What is manipulation?

Consists of creating levels of the independent variable, each level is a group, allows us to create groups to which participants will be randomly assigned

A history instructor tells his class the number of students who received an A on a recent exam. Inferential or Descriptive statistics?

Descriptive statistics

How would you find the interval width?

First determine the number of intervals in the frequency distribution (you decide this), then divide the real range by the number of intervals chosen: = real range/ number of intervals

The sample data from a poll are used to estimate the opinion of the population. Inferential or Descriptive statistics?

Inferential statistics

What is comparison/control

Involves the use of a comparison or control group that does not receive the manipulation believed to cause changes in a dependent variable

What is the mean?

It is the balance point or the average value in a data distribution. It is calculated by taking the sum of the scores and dividing it by the population or sample size

What is a nominal scale?

Measurements where a value is used to represent something or someone. These values are typically coded, or converted to numeric values for later statistical analysis. EX: A health psychologist studies food intake by recording two measures: the type of food consumed and the number of calories. The type of food consumed would be an example of this variable

What is an ordinal scale?

Measurements where values convey order or rank alone. This type of data indicates that one value is greater than or less than another value. Proficiency in mathematics graded in the categories of poor, fair, and good would be an example of this scale

What is an interval scale?

Measurements with two defined principles equidistant scales and no true zero. The IQ of your teachers would be an example of this scale

What is a ratio scale?

Measurements with two defining principles- equidistant scales and a true zero. EX: weight, height, time, calories

inferential statistics

Procedures used to infer or generalize observations made with samples to the larger population from which they were selected.

What are the three requirements of an experimental method?

Randomization, manipulation, and comparison

How to locate the interquartile range?

Remove the top and bottom 25%. Q3-Q1

What would n mean?

Sample size, a subset of all individuals belonging to a group of interest

What does s^2 symbolize?

Sample variance = Sum of squares/n-1

What is a continuous variable?

Such that they can be measured at any point beyond the decimal point. These can be measured in whole or fractional units.

What is the formula for Mw

Summation(M x n)/Summation n, weighted sum/combined n. M is the mean for each group, n is the sample size per group.

What is population variance?

The average squared distance of the deviation scores for an entire population from their mean. This can be calculated only when every score from the population is measured.

What is the correlation method?

The measurement of pairs of scores, called data points, examines the extent to which two variables are related. No variable is manipulated to create different groups to which participants can be randomly assigned. Instead two variables are measured for each participant, and the extent to which those variables are related is measured.

What is the median?

The midpoint of a data distribution such that half of the scores in a distribution occur above it and half below. It is located at the 50th percentile in a cumulative percent distribution. Scores MUST be in least to greatest order

What is a percentile rank?

The percentage of scores with values that fall below a specified score in a distribution.

What is a relative frequency?

The proportion of scores or values in each interval relative to all scores or values recored. To find, divide the frequency in a given interval by the total number of scores in the distribution: frequency in each interval/total count or frequency. This is converted into a RELATIVE PERCENT by multiplying the proportion by 100 to obtain a percentage.

What is the mode?

The score that occurs most frequently or often in a data set. It is most commonly used with the mean or median to describe central tendency

What is a cumulative frequency?

The sum of the frequencies of scores across a series of values or intervals. If calculated for all data in a distribution, will equal the total number of values or scores in a distribution

Dependent variable

The variable that is measured in each group or at each level of the independent variable. It must be operationally defined; it is defined by the specific process or manner by which it was observed or measured

What is there is an even number of scores in a distribution? (finding median)

Use n+1/2 to find the median position, take an average of those two scores (x+y/2). It will most likely be a .5 decimal.

What is randomization?

Uses random assignment to ensure that all participants in the study have an equal probability of being assigned to a group

What isa quasi-experimental method?

a research design that includes a variable with preexisting levels and or lacks a comparison/control group. An example of a variable with preexisting levels would be gender as the participants were men and women before the study began

What is the range?

a simple measure of variability and is the difference between the largest (L) and the smallest (S) scores in a distribution. = L-S, good measure of variability for data sets that do not have outliers and when the number of measured scores is small.

What does μ stand for?

population mean: Summation of X/ N

What does the symbol σ^2

population variance = Summation(x-μ)^2/ N or the Sum of Squares (SS)/N

descriptive statistics

procedures used to summarize, organize, and make sense of a set of scores called data. Typically presented graphically, in tabular form, or summary statistics

What is sample variance?

the average squared distance of the deviation scores for a sample from the sample mean and is calculated when you have measured only a portion or sample of scores from a large population.

What is variance?

the preferred measure of variability because all of the scores in the distribution are used in its calculation. Measures the average squared distance or deviation of scores from the mean. Deviation scores refer to the difference between a score and the mean