Week 11 Flashcards
What is a z-test
Hypothesis test used for a single mean if the sample is large enough and drawn at random
How do you find the z-test
- Specify the null and alternative hypothesis
- Specify the level of sampling error allowed
- Determine the sample standard deviation
- Calculate the estimated standard error of the mean using the formula
- State the result whether the null hypothesis can be rejected
What is a t-test
Hypothesis test used for a single mean if the sample is too small to use the z-test
How to do the t-test
- Specify the null and alternative hypothesis
- Specify the level of sampling error allowed
- Determine the sd
- Calculate the standard error
- Calculate the t-statistic
- State the result
How do you hypothesize about two means
- Specify the null and alternative hypothesis
- Set the level of sampling error
- Calculate the estimated standard error of the differences between the two means
- Calculate the test statistic Z
- State the result
What is an experiment
Research approach where one variable is manipulated and the effect on another variable is observed
What is experimental research referred to as
Causal research because it is the only type of research that has potential to demonstrate change in one variable
What are three things you must show in an experiment
- Correlation or concomitant variation
- Appropriate time order of occurencce
- Elimination of other possible factor
What are three types of evidence for causal relationships
- Correlation
- Appropriate time order of occurrence
- elimination of other possible causal factors
What are ways to show a causal relationship
- Correlation between two variables
- Showing that there is an appropriate time order of occurrence
- Eliminating other possible causal factors
What are laboratory experiments
Experiments conducted in a controlled setting
What are field experiments
Tests conducted outside the lab in an actual environment
What is validity
Defined as the degree to which an experiment actually measures what researchers was trying to measure
What is internal validity
Refers to the extent to which competing explanations for the experimental results observed can be ruled out
What is external validity
Refers to the extent to which the causal relationships measured in an experiment can be generalize to outside persons, setting and times
What is experimental notation
- X is used to indicate the exposure of an individual or a group to an experimental treatment
- O is used to refer to the process of taking measurements on the test units
- Different time periods are represented by horizontal arrangements
What are test units
Test units are individuals, groups of individuals or entities whose response to the experimental treatments is being tested
What are extraneous variables
Variables that pose a threat to experimental validity
What are some examples of extraneous variables
- History
- Maturation
- Instrument variation
- Selection bias
- Mortality
- Testing effects
- Regression to the mean
History
This is the intervention between the beginning and end of the experiment of any variable or event other than those manipulated by the researchers
Maturation
Refers to changes in subjects during the course of the experiment that are a function of time; it includes getting older, hungrier more, the like
Instrument variation
Refers to any changes in measurement instruments that might explain differences in the measurement taken
Selection bias
Is encountered in situations where the experimental or test group is systematically different from the population to which the researcher would like to project the experimental results or from the control group
What do researchers do to ensure equality of groups?
- Randomization involves assigning subjects to test groups and control groups at random
- Matching involves what the name suggests making sure that there is one to one match between people or other units in the test and control groups in regard to key characteristics
Mortality
Refers to the loss of test units during the course of an experiment
Why is mortality a problem
It is a problem because there is no easy way to know if the lost units would have respondent to the treatment variable in the same way as those units that remained throughout the entire experiment
Testing effects
Results from the fact that the process of experimentation can produce its own effect on the responses observed
What are main testing effects
Possible effects of earlier observations on later observations
What are interactive testing effects
The effect of prior measurement on the subjects response to a later measurement
What is the regression to the mean
Refers to the observed tendency of subjects with extreme behaviour to move toward the average for that behavior during the course of an experiment
What are four basic approaches used to control extraneous factors?
- Randomization
- Physical control
- Design control
- Statistical control
What is randomization
Carried out by randomly assigning subjects to treatment conditions so that extraneous causal factors related to subject characteristics can be assumed
Physical control
Extraneous causal factors involved holding constant the value or level of extraneous variables throughout the experiment
Design control
Control of extraneous factors by means of specific types of experimental designs developed for this purpose
Statistical control
Can be used to account for extraneous causal factors if these factors can be identified and measured throughout the course of the experiment
What is an experimental design
Test in which the researcher has control over and manipulates one or more independent variables
What do experimental designs include
- Treatment or experimental, variable (independent variable) that is manipulated
- Subjects who participate in the experiment
- Dependent variable that is measured
- Plan or procedure for dealing with extraneous causal factors
What is a treatment variable
The independent variable that is manipulated or changed
What is manipulation
Refers to the process which the researcher sets the levels of independent variable to test a particular causal relationship
What is experimental effect
The effect of the treatment variable on the dependent variable
What is contamination
Inclusion in a test group of a group of respondents who are not normally there
What are the problems that may occur in implementation
- Difficulty gaining cooperation within the organization
- Contamination problems
- Differences between test markets and total population
- Lack of an appropriate group of people or get geographic area of a control group
What are pre experimental designs
Often difficult to interpret because they offer little or no control of extraneous factors
What are one shot case study designs
Involves test units to the treatment variable for some period of time and then taking a measure of the dependent variables
What are the weaknesses in the one showcase study design
No pretest observations are made in the units that will receive the treatment and no control group oftest units that did not receive the treatment observed
What is one group pretest posttest design
Is the design employed most frequently for testing changes in established products or marketing strategies
What is true experimental design
The experimenter randomly assigns treatments to randomly selected test units
Why is randomization so important
This helps make the results of true experimental designs more valid than the results of pre-experimental designs
What is the principal reason for choosing randomized experiments
They clarify causal inference
