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Question:
What is statistical error, in what way it differs from a mistake?
Answer: Statistical error: A continuous variable can never be measured with perfect fineness because of certain habits and practices,
methods of measurements,
instruments used, etc. the measurements are thus always recorded correct to the nearest units and hence are of limited accuracy. In sta
tistics the error does not
mean mistake which is a chance of in accuracy because the actual or true values are, however, assumed to exist.
Question:
What is the difference between a nominal and an ordinal scale?
Answer: ORDINAL SCALE It includes the characteristic of a nominal scale and in addition has the property of ordering or ranking of me
asurements. For example, the
performance of students (or players) is rated as excellent, good fair or poor, etc. Number 1, 2, 3, 4 etc. are also used to indicate ranks
Question:
What is Finite population and Infinite population?
Answer: Finite Population: The population is Finite when it
contains countable number of units. Examples: 1.Population of all licensed cars. 2.Population of all students
in college. 3.Population of all houses in a country. Infinite Population: The population is Infinite when it contains uncountable number of units.
Examples:
1.Population of all points in line. 2.Population of pressures at various points in the atmosphere.
Question:
Which is better QUOTA SAMPLING or RANDOM SAMPLING?
Answer: Both Random & Quota sampling has their advantages & disadvantages. Both
are used by organizations for their surveys. 1.The main advantage of Random
sampling is that it provides a valid estimate of sampling error, But it is impossible to assess objectively the error in quot
a sampling. 2.When quota sampling is
cheap (and fast) it is usually done poorly. When it is done better, it is not all much cheaper really then efficient probability (Random) sampl
ing. Random
sampling is widely used in various areas such as industry, agriculture, business etc.
Question:
Define grouped data, ungrouped data and frequency.
Answer: Grouped data - Data available in class intervals as summarized by a frequency distribution. Individual values of the original data are not a
vailable. Or Data that
are presented in the form of frequency distribution
are called grouped data. We often group the data of a sample into intervals to produce a better over all
picture of the unknown population, but in doing so we lose the identity of individual observations in the sample. Ungrouped data - Ungrouped data is th
at in
which raw data is not grouped. Example: 2, 3, 9, 0, 4, 4, 1, 5, 4, 8, 5, 3, 6, 6, 0, 2, 2, 7, 6, 4, 8, 4, 3, 3, 1, 0, 8, 7, 5
, 1, 3, 4, 7, 2, 4, 7, 5, 2, 6, 3, 1, 7, 5, 4, 6, 4, 2,
5, 3, 4, Definition of frequency: Number of observations in each clas
s or group is called is the frequency of that class. It means “how frequently something
happens?”
Question:
In which situation we use Pie chart simple, Bar chart and multiple bar chart ?
Answer: Pie Chart consists of a circle divided into sectors whos
e areas are proportional to the various parts into which the whole quantity is divided. It is an effective
way of showing percentage parts when the whole quantity is taken as 100. It is also used when the basic categories are not quantifiable. For example
as with
expenditure, classified into food, clothing, fuel and light etc. Simple Bar Diagram is used when the data consist of a single
component and do not involve much
variation. Multiple Bar Diagram is used represent two or more related sets of data. It is a diagram which supplies more than one information at the same time.
Question:
Brifly decribe the primary data and secondary data.
Answer: Primary Data: Primary data are data collected by the investigators for the purposes of the study. This allows t
he opportunity to improve precision and to
minimize measurement bias through the use of precise definitions, systematic procedures, trained observers, and blinding duri
ng data collection. Such data are
usually expensive to acquire compared to secondary dat
a. Secondary Data: Secondary data are data collected for purposes other than that of the study, such as
patient clinical records, and are used frequently for case-control studies. Because the investigator has no control over definitions, collection procedu
res,
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