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AP Statistics Unit 3 Study Guide
Simulations Terms
simulation |
the imitation of chance behavior, based on a model that accurately reflects the experiment under consideration |
stopping rule |
"continue selecting until ..." |
How to Write Simulation Description
1. Select __ digit numbers to represent __. |
2. Let __ - __ represent ___ and let __ - __ represent ___. |
3. Select __ or Continue selecting ___ until ___. |
4. Record ___. |
5. Trial One : ___ ; Trial Two : ___ ; Trial Three : ___ |
Simulation Example
Alex needs a blood transfusion. She needs to find someone with B+ blood or she will die. 9% of all people have B+ blood. How many people on average would you need to check the blood type of until you find someone who can save Alex's life? |
1. Select 2-digit numbers to represent people |
2. Let 00-08 represent people with B+ blood and 09-99 represent people without B+ blood |
3. Continue selecting people until you find someone with B+ blood |
4. Record how many people you select before you find someone with B+ blood |
5. Trial One:6 ; Trial Two:16 ; Trial Three:15 |
Sampling Design Example
a college professor wants to survey a sample of students taking her large lecture course. There are about 150 students in the course, and 10 of those students are graduate students. She wants to take a systematic random sample of approximately 30 students. Which strategy will accomplish her intended design? |
randomly select one of the first 5 students to arrive to class, and every 5th student thereafter to take the survey. |
Biases
bias |
a systematic error in measuring the estimate that would repeatedly cause the data to be wrong |
voluntary response bias |
people select themselves to participate in the study |
nonresponse bias |
individuals who are randomly chosen for the sample cant be contacted or refuse to cooperate |
convenience sampling |
asking people who are easy to ask; convenient but not random |
under coverage bias |
some groups are left out of the selection process |
response bias |
the behavior of the respondent or interviewers causes you to get incorrect answers |
wording bias |
when wording of the question influences the answers that are given |
Bias Examples
voluntary bias |
online polls, facebook questionnaires |
nonresponse bias |
mailed polls, new apps on phone |
convenience bias |
friendly looking people, all people at the park |
under coverage bias |
only your neighborhood, phone books |
response bias |
cosplayer asking if people think cosplay is weird |
wording |
using strong vocabulary |
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Sampling Design Terms
population |
the entire group of individuals we want information about |
census |
a complete count of the population; when you gather general information about the entire population |
sample |
a part of the population we actually examine in order to gather information |
sampling design |
the method used to choose the sample from the population |
sampling frame |
a list of every individual in the population |
simple random sample |
every individual has an equal chance of being chosen |
stratified random sample |
population is divided into strata and then simple random sample is used on each stratum |
systematic random sample |
randomly select a number between one and n and survey every nth person after that |
cluster random sample |
randomly pick a location and sample all from that location |
multistage sample |
a combination of different sampling techniques |
How to Describe Sampling Design
simple random sample |
put the names/numbers of all ___ on slips of paper and place in a hat. Mix and randomly draw ___ slips of paper without replacement. Survey the corresponding people. |
systematic random sample |
number all ___ and place ___ numbers in a hat. Mix and randomly select one number and survey the corresponding person. Survey every nth person on the list after that. |
cluster random design |
number all clusters and put the numbers into a hat Mix and randomly select a number from the hat. Survey everyone in that cluster. |
stratified random sample |
sort everyone into strata then number ___ in all the stratum. place the numbers in a hat and draw __ numbers. survey the corresponding people in that specific stratum. repeat the process for all strata |
Experimental Design Types
completely randomized design |
experimental units are assigned completely at random to treatments |
randomized block design |
experimental units are blocked in homogeneous groups and then randomly assigned to treatments |
matched pairs design |
a special type of block design; match up experimental unit according to similar characteristics and randomly assign one to treatment A and the other get treatment B automatically |
Experimental Design Terms
observational study |
observe outcomes without imposing any treatment |
experiment |
actively impose a randomly assigned treatment in order to observe the response |
experimental unit |
the single individual to which the different treatments are randomly assigned |
factor / explanatory variable |
what we test or what we change |
level |
a specific value or type for the factor |
response variable |
what you measure or record at the end of the experiment |
treatment |
a specific experimental condition applied to the units |
control group |
a group that is used to compare the factor against; can be placebo |
placebo |
a "dummy" treatment that can have no physical effect; not required in every experiment |
blinding |
method used so that units or evaluators do not know which treatment units are getting |
double blinding |
neither the units nor the evaluators know which treatment a subject recieved |
confounding variable |
a third variable that potentially affects both the factor and the response variable |
Three Principles of Experimental Design
control the effects of extraneous variables on the response |
randomization used to assign subjects to treatments |
replication of the experiment on many subjects to quantify the natural variation in the experiment |
Completely Randomized Design
Experiment Example
A consumer group wants to test cake pans to see which works the best. It will test aluminum, glass, and plastic pans in both gas and electric ovens |
experimental unit: cake batter |
factors: material of pan & type of oven |
levels: aluminum, glass, or plastic & gas or electric |
response variable: evenness of cake |
amount of treatments: six |
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