stat 214 university of louisiana at lafayette test 1

statistics

procedure of collecting, analysing and concluding based on information

population

entire set of individuals about which information is sought

sample

the subject of the population which is actually being observed

types of sampling

simple random sampling. stratified sampling. sampling of convenience. cluster sampling. systematic sampling. voluntary response.

a statistic

a number that describes a sample

a parameter

is a number that discribes a population.

example: 57% of the teachers @ UL

answer: sample= the teachers . parameter= 57%

variable

characteristics of the individuals involved. types of data based on types of variables. Examples: majors, final score, grades (Qualitative & Quantitative)

Qualitative

classifies the individual into categories of Ordinal (natural order) & Nominal (no natural order)

Quantitative

tells how many or how much there is. dealing with #. Discrete ( can be listed) & Continuous ( involves decimals, not set)

frequency

the number of times a category appeared in data

frequency distribution

the table form of the data that presents each category with their frequency

relative frequency

the proportion of a category in the data.

the related frequency is calculated by

freq of category/ sum of freq *100

pareto chart

order bars from highest to lowest

continuous quantitative data

# divide the data into classes

skewed

to the left = negatively skewed

mode types

the peak (high point) UNImodel: one peak. MULTImodel: more than one peak

dot plot

useful for small data set

time series plot

used for large data set

leaf

the most right digit

stem

the rest of the digits excluding the most right digit

stem & leaf

useful compare two sets of data

mean

population mean U(mu) = Ex/N (E= summation, N= population size). basically the average

median

number that splits the data into half. if its even then take the average of the two most middle numbers.

is more resistant to extreme values than the mean

resistant

a statistic is said to be _______if it is not affected by the extreme values (small or large)

a long tail either left or right indicates

an extreme value ( to the left= small. to the right= large.)

mode

the value that appears most frequently in the data

variance

is a measure of how far the values in the data set are from the mean on the average

population variance

Population variance (σ2) tells us how data points in a specific population are spread out. It is the average of the distances from each data point in the population to the mean, squared.

standard deviation

population - σ= square root of σ squared.

there cannot be negative

variance or negative standard deviation