There are a number of sampling techniques to choose from for any study. List and
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Question
There are a number of sampling techniques to choose from for any study. List and describe at least 3 of these.
What are the levels of measurement of the data that you could collect from any study? List and define all of them, and give an example of each.
There are a number of descriptive statistics that could be used to describe data from a study. Name and define at least 5. Be sure to use complete definitions.
What are correlational statistics? Name the most common one and describe the meaning of the numbers that are related to this statistic.
What is meant by confidence interval?
In inferential statistics we find hypotheses about data. What is the null hypothesis?
What is meant by statistical significance?
What kind of tests could you run on data to determine if it is statistically significant? Name at least 3 tests, and tell me what they test.
Explanation / Answer
There are a number of sampling techniques to choose from for any study. List and describe at least 3 of these.
Sampling Methods can be classified into one of two categories:
Probability Sampling
In probability sampling it is possible to both determine which sampling units belong to which sample and the probability that each sample will be selected.
Methods :
Simple random sample :
It is easiest and most commonly used method of sampling. In this method each element of population is given same chance of getting selected in the sample. If population consists of N elements then probability of selecting any element at any draw is 1/N.
Stratified sampling :
If population is not homogeneous, SRS is not very effective. Therefore, the entire population is divided into several homogeneous groups called strata. A simple random sample of a suitable size is selected from each strarum and then combining these sampled observations we can form a sample. The sample is called stratified random sample.
Cluster sampling :
Sometimes population consists of several groups, which are convinient to use as sampling units. These groups are called as clusters. In cluster sampling, we consider cluster as sampling unit and choose simple random sample of clusters.
What are the levels of measurement of the data that you could collect from any study? List and define all of them, and give an example of each.
Level of measurement or scale of measure is a classification that describes the nature of information within the values assigned to variables
There are four levels of measurements :
a) Nominal scale
b) Ordinal scale
c) Interval scale
d) Ratio scale
Nominal scale :
It consists of two or more named categories into which the objects are classified.
ex. House number, survey number.
Ordinal scale :
It gives numbers to groups of objects using some quantifiable characteristics. Therefore ordered arrangement of groups is possible in this type of scale.
ex. groups of individuals according to income such as poor, middle class, rich.
Interval scale :
It has equal units of measurements, however, the zero point is arbitrary.
For example, when we measure temperature (in Fahrenheit), the distance from 30-40 is same as distance from 70-80. The interval between values is interpretable. Because of this, it makes sense to compute an average of an interval variable, where it doesn't make sense to do so for ordinal scales. But note that in interval measurement ratios don't make any sense - 80 degrees is not twice as hot as 40 degrees
Ratio scale :
It has equal units of measurements and those are taken from a true zero.
ex. the number of clients in past six months. Because you can have zero clients and because it is meaningful to say that "...we had twice as many clients in the past six months as we did in the previous six months."
There are a number of descriptive statistics that could be used to describe data from a study. Name and define at least 5. Be sure to use complete definitions.
Descriptive statistics are used to describe the basic features of the data in a study. They provide simple summaries about the sample and the measures. Together with simple graphics analysis, they form the basis of virtually every quantitative analysis of data.
The descriptive statistics are :
Mean
Median
Mode
Range
Inter quartile range
Mean is the average of the data. Mean is sum of observations divided by number of observations.
Median is the middle value of the data.
Mode in the most repeated observation in the data.
Range is the difference between largest observation and smallest observation.
Inter quartile range is defined as,
IQR = Q3-Q1
where Q3 is third quartile and
Q1 is first quartile.
What is meant by confidence interval?
In statistics, a confidence interval (CI) is a type of interval estimate (of a population parameter) that is computed from the observed data.
What is meant by statistical significance?
A result is statistically significant iff P-value of the test is less than level of significance.
Genereally we take level of significance as 5%.
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