Exam 1 Flashcards
measures the valve of the response variable without attempting to influence the value of wither the response or explanatory variables researcher observes the behavior of the individuals without trying to influence the outcome of the study
observational study
when the researcher signs the individuals in a study to a certain group, intentionally changes the value of the explanatory variable, and then records the value of the response variable for each group
designed experiments
a subset of a population
sample
the entire group to be studied
population
a person or object that is a member of the population being studied
individual
a numerical summary of a sample
statistic
consist of organizing and summarizing data
descriptive statistics
uses methods that take a result from a sample, extend it to the population, and measure the reliability of the result
inferential statistics
a numerical summary of a population
parameter
the characteristics of the individuals within the population
variables
allow for classification of individuals biased on some attribute or characteristic
qualitative, or categorical, variables
provide numerical measures of individuals; the values of this can be added or subtracted and provide meaningful results
quantitative variables
a way to look at and organize a problem so that it can be solved
approach
a quantitative variable that has either a finite number of possible values or a countable number of possible values; cannot take on every possible value between any two possible values
discrete variable
a quantitative variable that has a infinite number of possible values that are not countable; may take on every possible value between any two values
continuous variable
when the values of the variable name, label, or categorize; does not allow for the values of the variable to be arranged in a ranked or specific order
nominal level of measurement
a variable that has the properties of the nominal level of measurement, however the naming scheme allows for the values of the variable to be arranged in a ranked or specific order
ordinal level of measurement
a variable that has the properties of ordinal level of measurement and the differences in the values of the variable have meaning a value of zero does not mean the absence of the quantity; + and -
interval level of measurement
a variable that has rations of the values of the variable that have meaning; a value of zero means the absence of quantity; x and divide
ratio level of measurement
the information collected
explanatory variable
what is affected by the explanatory variable
response variable
this occurs in a study when the effects of two or more explanatory variables are not separated; meaning any relation that may exist between an explanatory variable and the response variable may be due to some other variable(s) not accounted for in the study
confounding
an explanatory variable that was not considered in a study, but it affects the value of the response variable in the study; typically related to explanatory variables considered in the study
lurking variable
These studies do not allow a researcher to claim causation, only association
observational studies
an explanatory variable that was considered in a study whose effect cannot be distinguished from a second explanatory variable in a study
confounding variable
these observational studies collect information about individuals at a specific point in time or over a very short period of time
cross-sectional studies
these observational studies are retrospective; look back in time or require the researcher to look at existing records; individuals who have a certain characteristic may be matched with those who do not
case-control studies
this observational study first identifies a group of individuals to participate in the study and then they are observed over a long period of time
cohort studies
a list of all individuals in a population along with certain characteristics of each individual
census
the process of using chance to select individuals from a population to be included in the sample
random sampling
a sample of size n from a population of size N is obtained through this if every possible sample size of size n has an equally likely chance of occurring
simple random sampling
the same that is taken from simple random sampling
simple random sample
the initial point for the generator to start creating random numbers
seed
an individual who is selected is removed from the population and cannot be chosen again
sample without replacement
a selected individual is placed back into the population and could be chosen a second time
sample with replacement
obtained by separating the population into non overlapping groups called strata and then obtaining a simple random sample from each stratum
stratified sample
obtained by selecting every kth individual from the population; the first individual selected corresponds to a random number between 1 and k
systematic sample
obtained by selecting al individuals within a randomly selected collection or group of individuals
cluster sample
a sample in which the individuals are easily obtained and not based on randomness
convenience sample
the individuals themselves decide to participate in a survey
self-selected convenience sample
lists each category of data and the number of occurrences for each category of data
frequency distribution
the proportion (or percent) of observations within a category
relative frequency
lists each category of data together with the relative frequency
relative frequency distribution
constructed by labeling each category of data on either the horizontal or vertical axis and the frequency or relative frequency of the category on the other axis
bar graph
a circle divided into sectors, where each sector represents a category of data; proportional to the frequency of the category
pie chart
categories into which data are grouped; used when using continuous data
classes
constructed by drawing rectangles for each class of data
histogram
the smallest value within the class
lower class limit
the largest value within the class
upper class limit
the difference between consecutive lower class limits
class width
a table is this if the first class as no lower class limit or the last class has no upper class limit; 40 or over
open ended
a way to represent quantitative data graphically; where the digits to the left of the rightmost digit form the stem; the rightmost digit forms a leaf
stem-and-leaf plot
created by placing each observation horizontally in increasing order and placing a dot above the observation each time it is observed
dot plot
when the frequency of each value of the variable is evenly spread out across the values of the variable
uniform distribution
when the highest frequency occurs in the middle and the frequencies tail off to the left and right of the middle
bell-shaped distribution
when the tail to the right of the peak is loonier than the tail to the left of the peak
skewed right
when the tail to the left of the peak is longer than the tail to the left of the peak
skewed left
the sum of consecutive lower class limited divided by 2
class midpoint
a graph that uses points, connected by line segments, to repress the frequencies for the classes
frequency polygon
displays the aggregate frequency of the category; discrete - displays he total number of observations less than or equal to the category; continuous - displays the total number of observations less than or equal to the upper class limit of a class
cumulative frequency distribution
displays the proportion (or percentage) of observations less than or equal to the category (discrete) or the upper class limit (continuous)
cumulative relative frequency distribution
a graph that represents the cumulative (relative) frequency for the class; plots points whose x-coordinates are the upper class limits and whose y are the cumulative (relative) frequencies
ogive
obtained by plotting the time in which a variable is measured on the horizontal axis and the corresponding value of the variable on the vertical axis; good for identifying trends over time
time-series plot
computed by adding all the values of the variable in the data set and dividing by the number of observations
arithmetic mean
computed using all the individuals in a population; µ
population arithmetic mean
computed using sample data; a statistic; x-bar
sample arithmetic mean
the value that lies in the middle of the data when arranged in ascending order; M
median
a numerical summary is said to be this if extreme values (very large or small) relative to the data do not affect its value substantially
resistant
the most frequent observation of the variable that occurs in a data set
mode
occurs when no observation occurs more than once
no mode
if a data set has 2 modes
bimodal
if the data set has three or more modes
multimodal
the degree to which the data are spread out
dispersion
the difference between the largest and the smallest data value
range; R
the ith observation minus the mean; the sum of all of these must equal zero
deviation about the mean
the square root of the sum of squared standard deviations about the population mean divided by the number of observations in the population, N
population standard deviation
the square root of the sum of squared deviations about the sample mean divided by n-1, where n is the sample size
sample standard deviation
the square of the standard deviation
variance
data that has been summarized in frequency distributions
grouped data
a value such as k percent of the observations are less than or equal to the value
kth percentile; Pk
divide data sets into fourths, or four equal parts
quartiles
divides the bottom 25% of the data from the top 75%; 25th percentile
first quartile, Q1
divides the bottom 50% of data from the top 50%; 50th percentile or the median
second quartile, Q2
divides the bottom 75% of the data from the top 25%; 75th quartile
third quartile, Q3
the range of the middle 50% of the observations in a data set; the difference between the third and first quartiles
interquartile range; IQR; IQR=Q3-Q1
extreme observations
outliers
serve as cutoff points for determining outliers
fences
the measure of the likelihood of a random phenomenon or chance behavior occurring
probability
short term results
outcomes
any process with uncertain results that can be repeated
experiment
the collection of all possible outcomes of a probability experiment
sample space, S
any collection of outcomes from a probability experiment; consists of one outcome or more than one outcome
event, E
lists the possible outcomes of a probability experiment and each outcome’s probability
probability model
when the probability of an event is 0
impossible
when the probability of an event is 1
certainty
an event that has a low probability of occurring; less than 0.05 or 5%
unusual event
when each outcome has the same probability of occurring
equally likely outcomes
