Studied by 38 people

5.0(2)

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hint

1

two types of studies

observational and experimental

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2

observational study

making observations with unmanipulated variables; making correlations

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3

experimental study

making observations with a manipulated variable; investigating cause and effects

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4

controlled experiment

changes one variable at a time

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independent / explanatory variable

variable being manipulated

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dependent variable / response variable

produces data necessary to support or refute hypothesis

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constants

aspects of the experiment kept the same

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8

confounding variable

a variable that links the independent and dependent variable and could be affecting the outcomes

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9

experimental units

objects being experimented on; humans referred to as subjects

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four principles of experimental design

comparison, random assignment, controls / constants, replication

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comparison

the experiment compares two or more treatments

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random assignment

using chance to assign treatments to groups

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13

controls / constants

variables kept the same in an experiment

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replication

using enough experimental units in an experiment

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15

placebo effect

any outcomes from the dummy treatment

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double-blind experiment

researcher and subject are unaware of which treatment is which

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population

entire group we want information about

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census

collects data from every individual in the population

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sample

subset of individuals from population which we actually collect data from

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convenience sample

choosing easy to reach individuals from the population

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voluntary response surveys

people decide whether to join the sample; creates bias since strong-opinioned people will only want to participate

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simple random sampling

every group of n individuals in population has an equal chance to be selected (hat method)

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stratified random sampling

classify population into homogenous groups (strata) and take SRS of them

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cluster sampling

classify groups into heterogenous groups (geographically) and take SRS of all the clusters; cluster chosen must be used

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systemic sampling

randomly choose starting point in population and select every kth member

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undercoverage

occurs when some members of the population could not be chosen

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nonresponse

when participant of experiment cannot be reached or refuses to participate

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response bias

the person asking questions could potentially affect data (systemic incorrect responses)

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wording of question

manner of question asked could potentially affect answer

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qualitative data

shown in bar graphs, frequency / relative frequency tables, pie chart

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quantative data

shown in histograms, stem plots, dot plots, box and whisker plots

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two-way table

two categorical variables organized according to a row and column variable

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marginal distribution

using the "margins" of the data

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mean

average of the data (use x with bar from sample mean and fancy u for population mean)

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median

midpoint of distribution when data is arranged smallest to largest

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interquartile range (IQR)

middle half of the data (Q3 - Q1)

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five number summary

minimum, Q1, median, Q3, maximum

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two ways to measure spread

IQR using quartiles and median; standard deviation using mean

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standard deviation

measures average distance of observations from mean; calculated by finding average of the squared distances and taking square root (s for sample and fancy o for population)

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skewed right

when data values are concentrated on left and less values are on the right; mean is greater than median (dinosaur tail points right)

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skewed left

when data values are concentrated in right and less values on the left; mean is less than median (dinosaur tail points left)

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symmetric

when data values are centered; mean and median is the same

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