stats research methods Flashcards
A sociologist proposes that the reason why people living below the poverty level have worse outcomes even for relatively minor health problems is because they have little or no access to adequate healthcare. In this situation, lack of access to healthcare is a(n) __________ variable.
A. moderator
B. mediator
C. control
D. outcome
B. mediator
Psychology 101 students are assigned ranks based on their total scores on a 50-item midterm exam. The ranks represent a(n) _____ scale of measurement.
A. nominal
B. interval
C. ratio
D. ordinal
D. ordinal
The mode, median, and mean for a distribution of final exam scores are 75, 50, and 35, respectively. Based on this information, you can conclude that this distribution is:
A. positively skewed.
B. negatively skewed.
C. leptokurtic.
D. platykurtic.
B. negatively skewed.
A school psychologist designs a study to determine if student gender and grade level are related to the number of interactions male and female teachers have with their students. This study has ___ independent variables and ___ dependent variable(s).
A. 2; 1
B. 2; 2
C. 3; 1
D. 3; 2
C. 3; 1
A distribution of scores has a mean of 60 and standard deviation of 5 and scores are normally distributed. Based on this information, you can conclude that about ___% of scores fall between the scores of 50 and 70.
A. 50
B. 68
C. 95
D. 99
C. 95
What is an independent vs dependent variable?
An independent variable is the variable that a researcher believes has an effect on the dependent variable.
What is a mediator vs moderator variable?
-affect the relationship between the study’s independent and dependent variables and make it difficult to determine if an apparent effect of an independent variable on a dependent variable is actually due to the independent variable.
-Mediator variable explains the relationship between independent and dependent variables. For instance, cognitive therapies are based on the assumption that therapy reduces anxiety because it alters client’s dysfunctional thinking. In other words, therapy (the independent variable) leads to more realistic thinking (mediator variable) which, in turn, leads to reduced anxiety (dependent variable).
What is an extraneous variable?
Affect the relationship between the study’s independent and dependent variables and make it difficult to determine if an apparent effect of an independent variable on a dependent variable is actually due to the independent variable.
What is nominal scale?
-divide people into unordered categories. Gender, eye color, and DSM diagnosis are nominal variables. Numbers can be assigned to the categories, but they’re just labels and do not provide any quantitative information.
1. qualitative
2. names, color, labels, etc.
3. order does not matter.
What is interval scale?
Variables measured on an ordinal scale divide people into categories that are ordered in terms of magnitude. (for example the WISC)
1. the order matters
2. differences dan be measured (except ratios)
3. not true 0 starting point.
What is ratio scale?
- the order matters
- differences dan be measured.
- contains a true 0 starting point.
what bar graphs are used for what?
bargraphs for nominal and ordinal
one dimensional
histograms for interval and ratio
two dimensional
frequency polygon(line graph) interval and ratio data
explain stardard deviation in a norm distribution
68 percent in 1 standard deviation—16-84
2 standard deviation is 4 to 95
3 standard deviation is 99 percent
positive and negatively skewed in terms of distribution of mode, medium and mean?
positive it goes mean median and mode
negative is goes mode, median, mean
lepokurtic and platykurtic peaks?
A leptokurtic distribution has a sharper peak and flatter tails than a normal distribution (i.e., most scores are “piled up” in the middle of the distribution). In contrast, a platykurtic distribution is flatter in the middle and has thicker tails than a normal distribution
——think plat means flat
Explain internal vs external validity?
Internal is to the study.
external is an application or generalization outside the study.
types of external validity?
population
ecological
temporal is generalizability of results over time
treatment
outcome is the generalizability of results to different but related dependent variables.
Threats to internal validity what does this mean?
it means factors of variable that could compromise the internal validity of the study?
Threat to internal validity History explain?
History refers to events that occur during the course of a study and are not part of the study but affect its results.
—-e.g. a power outage
Threat to internal validity maturation explain?
Maturation refers to physical, cognitive, and emotional changes that occur within subjects during the course of the study that are due to the passage of time and affect the study’s results
Threat to internal validity differential selection explain?
It occurs when groups differ at the beginning of the study due to the way they were assigned to groups and this difference affects the study’s results.
Threat to internal validity statistical regression explain?
threatens a study’s internal validity when participants are selected for inclusion in the study because of their extreme scores on a pretest. It occurs because many characteristics are not entirely stable over time and many measuring instruments are not perfectly reliable
Threat to internal validity testing explain?
Testing threatens a study’s internal validity when taking a pretest affects how participants respond to the posttest.
Threat to internal validity instrumentation explain?
when the instrument used to measure the dependent variable changes over time. For example, raters may become more accurate at rating participants over the course of the study.