Stat Exam 1

A psychologist wants to know if adults with normal vision can be fooled by a certain optical illusion. She recruits 50 students from a list of students in her PSY 120 class and finds that 42 of them are fooled by the illusion

The population in this study is?
a. all students in the PSY 120 class
b. all adults with normal vision
c. the 42 students who were fooled
d. the 50 students who served as subjects
e. a list of students in her PSY 120 class
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A psychologist wants to know if adults with normal vision can be fooled by a certain optical illusion. She recruits 50 students from a list of students in her PSY 120 class and finds that 42 of them are fooled by the illusion

The population in this study is?
a. all students in the PSY 120 class
b. all adults with normal vision
c. the 42 students who were fooled
d. the 50 students who served as subjects
e. a list of students in her PSY 120 class
b. all adults with normal vision
A psychologist wants to know if adults with normal vision can be fooled by a certain optical illusion. She recruits 50 students from a list of students in her PSY 120 class and finds that 42 of them are fooled by the illusion

Identify the sample for this survey.
a. all students in her PSY 120 class
b. all adults with normal vision
c. the 42 students who were fooled
d. the 50 students who served as subjects
e. a list of students in her PSY 120 class
d. the 50 students who served as subjects
A psychologist wants to know if adults with normal vision can be fooled by a certain optical illusion. She recruits 50 students from a list of students in her PSY 120 class and finds that 42 of them are fooled by the illusion

What is the parameter?
a. all students in the PSY 120 class
b. all adults with normal vision
c. the 42 students who were fooled
d. the 50 students who served as subjects
e. a list of students in her PSY 120 class
b. all adults with normal vision
A psychologist wants to know if adults with normal vision can be fooled by a certain optical illusion. She recruits 50 students from a list of students in her PSY 120 class and finds that 42 of them are fooled by the illusion

What is the statistic?
a. all students in the PSY 120 class
b. all adults with normal vision
c. the 42 students who were fooled
d. the 50 students who served as subjects
e. a list of students in her PSY 120 class
c. the 42 students who were fooled
A psychologist wants to know if adults with normal vision can be fooled by a certain optical illusion. She recruits 50 students from a list of students in her PSY 120 class and finds that 42 of them are fooled by the illusion

What is the sampling frame?
a. all students in the PSY 120 class
b. all students with normal vision
c. the 42 students who were fooled
d. the 50 students who served as subjects
e. a list of students in her PSY 120 class
e. a list of students in her PSY 120 class
Odero wants to take an SRS of 15 of the 50 students who reside in a large college dormitory. He labels the students 01 to 50 in an alphabetical order. In the table of random digits he read the entries:

38448 48789 18338 24697 39364 42006 76688 08708

The first four students in your sample have labels?
38, 44, 18, 33
Population
In a statistical study is the entire group of individuals about which we want info
Sample
is the part of the population from which we actually collect info and is used to draw conclusions (statistical-inference) about the population
Sampling
is the way we select a sample from a population
simple random sampling
every member of the population has an equal probability of being selected for the sample

produces unbiased estimates
voluntary response samplingChoose itself by responding to a general appeal. Examples include: write-in or call-in option pollsstratified random samplingcategory or group it means we want to divide divide the sampling frame into groups of individuals, called strata. Strata could be formed by gender, race, income, class, majorcluster samplingfor efficiency arises in two steps: Divide the sampling frame into clusters and take a SRS of clusters sample every individual in each cluster selectedConvenience sampleSampling those that are the easiest to reach, you exclude many groups of individuals (under coverage is the main problem with convenience samples)random sampling erroris the deviation between the statistic and the parameter caused by chance in selecting a random sample. The margin of error in a confidential statement accounts/includes only the random sampling error. The main source of sampling error: 1. small sample size 2. bad sample size -voluntary response sampling -connivence sampling 3. if by any change, the sample is "unlike" the population, we are likely to experience a random sampling errornonsampling errorserrors that arise from sources not related to the act of sampling. They can be present even in a census. Nonsampling error can occur in all aspects of the survey process. For example: frame errors/coverage errors Here are some sources of nonsampling error: -Data entry/processing errors -non-response failure to obtain data from an individual selected from a sample. Most nonresponse occur when some subjects cannot be contacted or because some subjects who are contacted refuse to cooperate -Response error: occurs when a subject gives an incorrect response (participant lies about his/her response)Response variablea variable that measures the major outcome or result of a studyExplanatory variablea variable that we think may explain or cause a change in the response variableLurking variablea variable that has an important effect on the relationship among the variables in a study but is not one of the explanatory variables studiedConfounding variablestwo variables are confounded when their effects on the response variable cannot be distinguished from each otherRandomizationrandomize as much as possible to reduce/head off selection biasReplicationuse enough subjects to reduce the effect any one subject has on the resultsControlus a control group to keep lurking variables at bayrandomized comparative experimentan experiment that compares the effect of two or more treatments and also randomly assigned subjects to the different treatmentsSub categories of randomized comparative experiments1. completely randomized design 2. matched pairs design 3. block designCompletely randomized designeach subject in a completely randomized design is assigned one of any of the possible groups at random we always determine in advance how large each group should bematched pairs designappropriate when comparing two treatments subjects are paired up so that the two subjects in each pair are similar in some critical way