Stats Test #1
discrete variable
by counting isolated points (not connected)
mid range
largest - smallest / 2 only use when the smallest and largest values are the only option of study
dispersion
measures the spread of a data set
(T/F) If the total number of observations are the same for all the data sets then either a frequency side by side bar graph or a R.F side by side bar graph is appropriate?
TRUE
(T/F) There may be infinite possible values for a discrete variable?
TRUE
(T/F) median is noT affected by the outliers?
TRUE
continuous variable
by measurement of intervals (all connected)
side by side bar graph
if there are two or more data sets involved in a QUALITATIVE variable
Decide whether the specified study is descriptive or inferential? An epidemiologist estimates the percentage of Californians who smoke
inferential
range in dispersion
largest - smallest
Range
largest - smallest ex. 94-54= 41, 41 is the range
mode = which dispersion?
none
ex of identifying the variable of interest:
of a population of people who are left handed- variable is: if a person is left handed
median
"open ended" distribution. the value occupies the middle portion when the data set is IN ORDER
Histogram provides what?
the shape of a distribution and more information
standard deviation or variance
the study of how spread out the numbers are
qualitative variable
can be placed into distinct CATEGORIES (can't put a #) ex: gender
what is the reason for a side by side bar graph?
to compare the groups
what is the purpose of a sample?
to make inference about the population
what was the purpose of the "counting G's" activity done in class?
to show the population is not always as trust worthy as the sample
Mode
use when qualitative. the most frequent value in the category (doesn't have to have a mode)
mean = which dispersion?
variance/ standard deviation
when do you use the grouped frequency/ R.F distribution?
when the RANGE of the data is too large to list all the observations ex. 0-100 students in a class, group by 0-20, 21-40, 41-50...etc..
what is a "bad" sample?
when the sample does not represent the population
Designed experiment
1. compare treatments and control 2. observe characteristics 3. take measurements (establish causation)
2 parts of a quantitive variable
1. discrete 2. continuous
Observational study
1. observe the characteristics (do not touch) 2. take measurements (only reveal association)
what are the 2 variable parts?
1. qualitative 2. quantitive
Dispersion measures of a spread:
1. range 2. variance or standard deviation 3. IQR(inter quartile range)
How to describe a data set?
1. shape 2. central tendency 3. dispersion
variable
CHARACTERISTIC of interest for each INDIVIDUAL element in the group
(T/F) A data set is given as follows: 2, 2, 2, 3, 3, 5, 5, 3, 5. The mode for this data set includes 2, 3, and 5?
FALSE
(T/F) bar graph can be used to summarize information for a quantitative data set?
FALSE
(T/F) even though the range of the data set is large, we can still use the ungrouped frequency distribution to summarize the data as long as the data set is very small?
FALSE
(T/F) if a quantitive variable has infinite possible values, it must be a continuous type?
FALSE
(T/F) in a simple random sampling, a "bad" sample is impossible of being selected?
FALSE
(T/F) possible values of a discrete variable have to be whole numbers?
FALSE ( just need to be isolated points, not whole numbers)
median = which dispersion?
IQR (inter quartile range)
Is an example of a zip code a qualitative variable or quantitative?
Qualitative because it is not reasonable to compare zip codes, it is to indicate an area
Qualitative data and Quantitative data
Qualitative data= tables and graphs Quantitative data= histogram
mid range = which dispersion?
Range
(T/F) If the total number of observations are different then only the R.F side by side bar graph is appropriate?
TRUE
sample
a subsect of a population (not everyone) (selected, studied, interviewed)
mean of the average
add all the numbers together and then divide by the amount of numbers there are ex. (13 + 18 + 13 + 14 + 13 + 16 + 14 + 21 + 13) ÷ 9 = 15
population
consists of ALL of the numbers in the group of interest (everyone)
inferential statistics
consists of methods to allow us to study a sample and then make inference about the population
Decide whether the specified study is descriptive or inferential? As part of the graduation paperwork, seniors at particular college were asked to indicate their post-graduation plans. Results showed that 15% planned to start graduate school right after college graduation
descriptive
2 types of statistics:
descriptive and inferential
Simple Random Sampling (SRS)
each of the possible sample of a given size has an equal chance to be obtained/selected
starting point
equal or little less than the smallest observation. Is the lower boundary of the first class ex. starting point= 5 class width= 10 5-< 15 15-<25 25-<35
Bar graph
for qualitative variables need to put spaces in between bars and can be put in any order
what is required in a table?
frequency distribution( #of occurrences) and relative frequency distribution RF=F/N
quantitive variable
ia numerical in nature and can be counted ex: gram
central tendency
identify a single value as the representative for the entire data set: mean of the average median mode mid range
Is this variable quantitive or qualitative? Number on a football player's jersey
qualitative
Is this variable quantitive or qualitative? A monthly telephone bill (in dollars)
quantitive discrete
descriptive statistics
simplify and present data