STA301 Definition Notes by Junaid

Definitions · LECTURE 01 TO 22 · Statistics:

Statistics is that science which enables to draw conclusions about various phenomena one the basis of real data collected on sample basis. OR

Statistics is a science of facts and figures.

INFERENTIAL STATISTICS:

That branch of Statistics which enables us to draw conclusions or inferences about various phenomena on the basis of real data collected on sample basis.

Data:

A well defined collection of objects is known as data.

Qualitative data:

Data that are labels or names used to identify an attribute of each element. Qualitative data may be nonnumeric or numeric.

Qualitative variable:

A variable with qualitative data.

Quantitative data:

Data that indicate how much or how many of something. Quantitative data are always numeric.

Variable:

A measurable quantity which can vary from one individual or object to another is called a variable.

Nominal Scale:

The classification or grouping of observations into mutually exclusive qualitative categories is said to constitute a nominal scale e.g. students are classified as male and female.

Ordinal Scale:

It includes the characteristic of a nominal scale and in addition has the property of ordering or ranking of measurements e.g. the performance of students can be rated as excellent, good or poor.

Interval Scale:

A measurement scale possessing a constant interval size but not true zero point is called an Interval Scale.

Ratio Scale:

It is a special kind of an interval scale in which the scale of measurement has a true zero point as its origin.

Biased Errors:

An error is said to be biased when the observed value is consistently and constantly higher or lower than the true value.

Unbiased Errors or Random Errors:

An error, on the other hand, is said to be unbiased when the deviations, i.e. the excesses and defects, from the true value tend to occur equally often.

Primary Data:

The data published or used by an organization which originally collected them are called primary data thus the primary data are the first hand information collected, complied, and published by an organization for a certain purpose.

Secondary Data:

The data published or used by an organization other than the one which originally collected them are known as secondary data.

DIRECT PERSONAL INVESTIGATION:

In this method, an investigator collects the information personally from the individuals concerned. Since he interviews the informants himself, the information collected is generally considered quite accurate and complete.

INDIRECT INVESTIGATION:

Sometimes the direct sources do not exist or the informants hesitate to respond for some reason or other. In such a case, third parties or witnesses having information are interviewed.

Population:

The collection of all individuals, items or data under consideration in statistical study is called Population.

Sample:

A sample is a group of units selected from a larger group (the population). By studying the sample it is hoped to draw valid conclusions about the larger group. OR

Sample is that part of the Population from which information is collected.

SAMPLING FRAME:

A sampling frame is a complete list of all the elements in the population.

Sampling Error:

The sampling error is the difference between the sample statistic and the population parameter.

Non-Sampling Error:

Such errors which are not attributable to sampling but arise in the process of data collection even if a complete count is carried out.

Sampling with replacement:

Once an element has been included in the sample, it is returned to the population. A previously selected element can be selected again and therefore may appear in the sample more than once.

Sampling without replacement:

Once an element has been included in the sample, it is removed from the population and cannot be selected a second time.

Standard error:

The standard deviation of a point estimator. AND The degree of scatter of the observed values about the regression line measured by what is called standard deviation of regression or standard error of estimate.

Sampling Unit:

The units selected for sampling. A sampling unit may include several elements.

NON-RANDOM SAMPLING:

Nonrandom sampling’ implies that kind of sampling in which the population units are drawn into the sample by using one ’s personal judgment. This type of sampling is also known as purposive sampling.

Quota Sampling:

Quota sampling is a method of sampling widely used in opinion polling and market research. Interviewers are each given a quota of subjects of specified type to attempt to recruit for example, an interviewer might be told to go out and select 20 adult men and 20 adult women, 10 teenage girls and 10 teenage boys so that they could interview them about their television viewing.

RANDOM SAMPLING:

The theory of statistical sampling rests on the assumption that the selection of the sample units has been carried out in a random manner. By random sampling we mean sampling that has been done by adopting the lottery method.

Simple random sampling:

Finite population: a sample selected such that each possible sample of size n has the same probability of being selected. Infinite population: a sample selected such that each element comes from the same population and the elements are selected independently.