Baylor University QBA 2302 Exam 1
interquartile range
Q3-Q1, used to determine which points are outliers
statistic
a numerical measure of all elements within a sample
convenience sample
a sample that is easy to obtain. DISADV: not SRS and not representative, ie surveys on thee internet
what is a representative sample
a sample that represents the population well
what is a srs
a sample where every single element in a population has the exact same chance of being chosen. DISADV: sometimes SRS might meet criterion ie. 40% male and 60% female and thus not always a rep sample
what is a population
a set of ALL individuals or items being studied, when defining a population include the word ALL
sample
a subset of individuals from a population, use the word SOME. big data=big sample
stratified sampling
a variation of random sampling; the population is divided into subgroups and weighted based on demographic characteristics of the national population ADV: a rep sampling, ie NYC is made of 5 boroughs
is a representative sample biased
can be called unbiased
systematic sampling
choosing every kth personm
what are the two types of quantitative variables
discrete and continuous
what is the formula and notation for SAMPLE variance
s2
what is a discrete variable
set is finite and limited number of outcomes, "counting data"
what is the best data collection method
simple random sample
biased sample
some portions have a greater chance of being chosen,
cluster sampling
split the population into different mutally exclusive and collectivly exhaustive groups and then take a random sample from only SOME of the groups.. ADV: a good way to keep from a biased sample when pop is geographically large DISADV: not representative or SRS
descriptive statistics
summarizes a data set, ie mean median mode range, GRAPHS
bar graphs
summarizes qualitative data, bars are touching
pie chart
summarizes qualitative data, do not use when there are many slivers
Box plot
summarizes quantative data
histogram
summarizes quantitative data, like a bar graph but bars arent touching
stem and leaf plot
summarizes quantitative data, use if you dont have a lot of numbers, we can see which numbers show up frequently
standard deviation
the square root of the variance, for nation just square root o2 or s2, an outlier can throw off
what is statistics for
to understand and analyze data in the real world
continuous data
too many outcomes to list out, measurable
what is unamodel, bimodel, multimodel
unamodel: one peak or mode bimodel: two peaks same hieght multimodel: more than 2 of same height peaks
inferential stats
use a summary measure from a data set to make an inference for an entire population, NOT graphs, it is making an inference will include a thus statement
what is a variable
varies from element to element, where we obtain data, qualitative or quanitative
non-response bias
when individuals selected to be in the sample do not respond
what is distribution
where points tend to fall on a number line
what is the variance
• Most frequently used measure of variability • Mean of the squares of deviation scores • basically an average distance of data points away from the mean always positive
semiquartile
IQR/2
what does empirically based mean
based on data and everything is empirically based
voluntary response
bias because self selected
leading questions
bias because wording favors a response ie, satisfied, very satisfied
what is the tendency of j shape
higher numbers get more frequent
what is a measure of variation
how spread out the numbers are ie, range , variance
what is the mode
inconsistant, may be several modes or no modes, not mathematically tactable, ONLY measure of central tendency that can be used with qualitative data
what is a bias sample
leaves out certain portions which reflects in inaccurate view
what is left skewed and right skewed
left skewed: higher numbers are more frequent right skewed: lower numbers are more frequent
dot plot
like a stem and leaf plot but has dots
percentiles
measure of variation, quartiles of 25
social desirability
most like to be seen in good light so may not be honest particularly if survey results are not confidental
what is the range
not mathematically tractable, not consistent, and bad if there are outliers
what is a parameter
numerical measure of all elements in a population, actually impossible to find
what is the formula and notation for POPULATION variance
o2
what is an element
one thing in a population, in real life we cannot track down data from all elements in an entire population
we use statistics to estimate....
parameters