BUSTAT Descriptive Stats part1

ppt ni sir

population

population

is the collection of all items of interest or under investigation

sample

is an observed subset of the population

parameter

is a specific characteristic of a population

values calculated using population data

statistic

is a specific characteristic of a sample

values computed from sample data

simple random sampling

is a procedure in which

• each member of the population is chosen strictly by chance

• each member of the population is equally likely to be chose and

• every possible sample of n objects is equally likely to be chosen

the resulting sample is called a random sample

descriptive statistics

collecting, summarizing, and processing data to transform data into information

inferential statistics

provide the basis for predictions, forecasts, and estimates that are used to transform information about samples into inferences about populations

inference

is the process of drawing conclusions or making decisions about a population based on sample results

decision making process

• identify the problem

1. data

   • descriptive statistics, probability, computers

2. information

   • experience, theory, literature, inferential statistics, computers

3. inferences

4. decision

pareto diagram

• used to portray categorical data

• a bar chart, where categories are shown in descending order of frequency

• a cumulative polygon is often shown in the same graph

• used to separate the “vital few” from the “trivial many”

line chart

• is used to show the values of a variable over time

• time is measured on the horizontal axis

• the variable of interest is measured on the vertical axis

frequency distribution

is a list or a table containing class groupings (categories or ranges within which the data fall) and the corresponding frequencies with which data fall within each class or category

frequency distribution

is a way to summarize data, the distribution condenses the raw data into a more useful form, and allows for a quick visual interpretation

histogram

a graph of the data in a frequency distribution is called a ______. the interval endpoints are shown on the horizontal axis. the vertical axis is either frequency, relative frequency or percentage. bars of the appropriate heights are used to represent the number of observations within each class

symmetric

the shape of the distribution is said to be ____ if the observations are balanced, or evenly distributed, about the center

skewed

the shape of the distribution is said to be ____ if the observations are not symmetrically distributed around the center

positively skewed

a _______ distribution (skewed to the right) has a tail that extends to the right i the direction of positive values

negatively skewed

a _______ distribution (skewed to the left) has a tail that extends to the left i the direction of negative values

scatter diagrams

are used for paired observations taken from two numerical variables

• one variable is measured on the vertical axis and the other variable is measured on the horizontal axis

cross tables

(or contingency tables) list the number of observations for every combination of values for two categorical or ordinal variables