review for psych ch 1-3

statistics

set of mathematical procedures for organizing, summarizing, and interpreting information

population

set of all the individuals of interest in a particular study

sample

set of individuals selected from a population

variable

characteristic or condition that changes or has different values for different individuals

steps to an experiment

1. experiment - comparing two studying methods

   • attain data: test scores for each student in each example

2. descriptive statistics: organizing and simplifying: average? mode?, it is the procedures used to summarize, organize, and simplify data

3. inferential : what does this mean? what can we generalize

statistic

value, usually a numerical value, that describes a sample

parameter

value of numbers that describes a population

• A characteristic that describes a population— the average score for the population

inferential statistics

techniques that allow us to study samples and then make generalizations about populations

descriptive statistics

it is the procedures used to summarize, organize, and simplify data

sampling error

discrepancy that occurs naturally and exists between a selection statistic and the corresponding population parameter

correlational method

technique wherein two different variables are observed to determine whether they are related

experimental method

technique in which one variable is manipulated while another variable is observed and measured

nonequivalent groups study

research in which collections of participants are formed without the researcher controlling assignment

quasi independent variable

groups of scores that are examined for their influence on a dependent variable

ex. boys vs girls, old vs young

constructs

internal attributes or characteristics that cannot be directly observed

operational definition

explanation describes a construct in terms of how it is measured

discrete variable

scale consisting of separate, indivisible categories

• planets around the sun

• how many students are in a class

whole, countable numbers—for example, the number of children in a family or the number of students attending class

continuous variable

scale for which there are an infinite number of possible values

• height of students in class

• amount of stars in the galaxy

• weight

can be measured in a continuous line

real limit

boundaries of intervals for scores that are represented on a continuous number line

upper real limit

boundary that separates an interval from the next higher interval

lower real limit

boundary that separates an interval from the next smaller interval

ordinal scale

set of categories that are ranked in terms of size or magnitude

interval scale

ordered categories that are all spaced exactly the same size

data set

is a collection of measurements or observations.

datum

is a single measurement or observation and is commonly called a score or raw score.

what can population refer to ?

it can refer to both people itself, and the population of scores

characteristics

characteristic that describes population: parameter

characteristic that describes sample: as statistic

what is the margin of error

the sampling error

participant variables

These are characteristics such as age, gender, and intelligence that vary from one individual to another

environmental variables

These are characteristics of the environment such as lighting, time of day, and weather conditions

3 basic techniques to control variables

1. random assignment

2. matching (equally controlled environments) eg. matching % of ppl under a specific condition

3. holding them constant, holding gender and age constant so that it doesn’t influence the dependent variable

the independent variable

the variable that is manipulated by the researcher.

• usually consists of the two (or more) treatment conditions to which subjects are exposed.

• consists of the antecedent conditions that were manipulated prior to observing the dependent variable.

nonexperimental, quasi design

compares preexisting groups, the researcher cannot control the assignment of participants to groups and cannot ensure equivalent groups

in non experimental study design, what is the independent variable also referred to as

the quasi-independent variable.

In a correlational study, how many variables are measured for each individual and how many groups of scores are obtained?

2 variables and 1 group

things to note about continuous variables

1. very rare to obtain identical measurements for two different individuals. Because a continuous variable has an infinite number of possible values, it should be almost impossible for two people to have exactly the same score

2. each measurement category is actually an interval that must be defined by boundaries. For example, two people who both claim to weigh 150 pounds are probably not exactly the same weight. However, they are both around 150 pounds. One person may actually weigh 149.6 and the other 150.3

boundaries of intervals for scores that are represented on a continuous number line

real limits: there also exists an upper real limit and a lower real limit

should 150.5 be assigned to the 150 interval or the 151 interval?

either. It is a boundary boundary the two intervals and is not necessarily in one or the other.

placement of 150.5 depends on the rule that you are using for rounding numbers: rounding up, then 150.5 goes in the higher interval

rounding down, then it goes in the lower interval .

what does the term discrete and continuous apply to

the terms continuous and discrete apply to the variables that are being measured and not to the scores that are obtained from the measurement

score

X

N

identifies the number of scores in a population

n

identifies the number of scores in a sample

Descriptive statistics are generally used for

simplifying and summarizing data

• doesnt apply only to dependent nor independent variables

real limit precision for precision scale of 0.2

divide 0.2 into 2 → 0.1 so real limit is 0.1 above and below score

real limit precision for precision scale of 0.1

divide 0.1 into 2 → 0.05 so real limit is 0.05 above and below score

frequency distribution

an organized tabulation of disorganized set of scores and places them in order from highest to lowest, grouping together individuals who all have the same score

organizes the number of individuals located in each category on the scale of measurement

goal is to see at a glance

range

distance from the highest score to the lowest score

apparent limits

values of scores that are highest and lowest in an interval

class interval

group of scores in a grouped frequency distribution

histogram

graph showing a bar above each score or interval

grouped frequency distribution

chart wherein scores are collected into intervals rather than as individual values

polygon

graph consisting of a line that connects a series of dots

relative frequency

proportion of the total distribution, rather than the total number of times the event occurred

tail

section wherein the scores taper off toward one end of a scale

skewed distribution

occurance of the scores tending to pile up toward one end of a scale

• positively skewed: occurance wherein the scores pile up on the left side of a scale

• negatively skewed: occurance wherein the scores pile up on the right side of a scale

rank

percentage of individuals in the distribution with scores at or below the particular value

percentile

score that is identified by its relative position in a distribution

repeated measures design

study wherein the scores are all obtained from the same group of participants

mode

most frequent score

weighted mean

average of two averages, handicapped by the number of scores they represent