Introduction to Biostatistics: Part 1 Week 2

Probability or non-probability sampling? -Cluster sampling

Probability

Probability or non-probability sampling? -Multistage sampling

Probability

Probability or non-probability sampling? -Simple random sampling (SRS)

Probability

Probability or non-probability sampling? -Stratified sampling

Probability

Example of Inferential statistics

"Measure the impact of new depression drugs effectiveness." -Take 100 people with depression, and split them up into two groups randomly. -With the first group, give them a sugar pill, and give the second group a new depression drug. -If you find a statistically significant difference, you infer that you would find similar results in the population. (Example of a random clinical trial)

What are the 4 types of non-probability sampling?

-Convenience Sampling -Purposive Sampling -Quota Sampling -Referral /Snowball Sampling

What are 5 probability Sampling techniques?

-Simple random sampling -Stratified sampling -Systematic sampling -Cluster sampling -Multistage sampling

What type of variable? -Observations can take a value that can be logically ordered or ranked. The categories associated with ______ variables can be ranked higher or lower than another, but do not necessarily establish a numeric difference between each category. -Examples: academic grades (i.e. A, B, C), clothing size (i.e. small, medium, large, extra large) and attitudes (i.e. strongly agree, agree, disagree, strongly disagree).

Ordinal

A _______ is a complete set of persons, scores, objects having a common observable characteristic.

Population

Probability or non-probability sampling? -Systematic sampling

Probability

What are the two main branches of sampling strategies?

Probability and non-probability sampling

Each member has a fixed, known opportunity to belong to the sample. The probability of any member of the sample group being selected for the sample can be mathematically calculated.

Probability sampling

Is probability or non-probability sampling more representative of the population?

Probability sampling

This is an example of what type of sampling? -A large company surveys 100 employees by taking random samples from 10 managers and 90 non-managerial employees. A.Simple random sample B.Stratified random sample C.Cluster random sample D.None of the above

B

What type of variable? -When there are only two possible levels. These variables can usually be phrased in a "yes/no" question. -Examples: male or female, true or false

Binary

This is an example of what type of sampling? -A principal orders t-shirts and wants to check some of them to make sure they were printed properly. She randomly selects 22 of the 100 boxes of shirts and checks every shirt in those 22 boxes. A.Simple random sample B.Stratified random sample C.Cluster random sample D.None of the above

C

What type of variable? -Have values that describe a 'quality' or 'characteristic' of a data unit, like 'what type' or 'which category'.

Categorical

What type of sampling? -The entire population is divided into groups/sections and then the groups are randomly selected. -All the elements of the group are used for sampling. Groups are identified using details such as age, sex, location etc.

Cluster sampling

What type of variable? -Observations can take any value between a certain set of real numbers. The value given to an observation for a _______ variable can include values as small as the instrument of measurement allows. -Examples: height, time, age, and temperature.

Continuous

What type of sampling? -This method is used when the availability of sample is rare and also costly. So based on the easy accessibility, samples are selected -For example: Researchers prefer this during the initial stages of survey research, as it's quick and easy to deliver results. -Second example: A teacher wants to know what types of classes students enjoy taking most. To make it easier, the teacher asks the first 15 people that arrive to class.

Convenience sampling

Lilian's favorite magazine published 50 issues last year, and each issue contained approximately 250 pages. She wants to take a cluster random sample of about 1,000 total pages to estimate what proportion of all pages contained an advertisement. *Which of these strategies will accomplish her intended design?* A. Examine the first 50 pages in the 20 most recent issues. B. Put the issues in a random order and examine every10th page until 1,000 pages have been examined. C. Assign a unique number to each page, and use a computer to randomly select 1,000 of those numbers. D. Randomly select 4 issues, and examine every page in those issues. E. Examine 20 randomly selected pages from each of the 50 issues.

D

What type of sampling? -It is the combination of one or more probability sampling methods. -Population is divided into multiple clusters -These clusters are further divided and grouped into various sub groups (strata) based on similarity -One or more clusters can be randomly selected from each stratum. This process continues until the cluster can't be divided anymore. For example country can be divided into states, cities, urban and rural and all the areas with similar characteristics can be merged together to form a strata.

Multistage sampling

What type of variable? -Observations can take a value that is not able to be organized in a logical sequence. -Examples: sex, business type, eye color, religion, and brand.

Nominal

What are the three types of categorical variables?

Nominal, ordinal, binary

There is no specific probability of an individual to be a part of the sample

Non-probability sampling

What SPSS variable? -Only numbers and are suitable for numeric calculations such as addition and multiplication.

Numeric

What type of variable? -Describe a measurable quantity as a number, like 'how many' or 'how much

Numeric

What are the two main branches of variables?

Numeric and categorical

What are the two variables in SPSS?

Numeric and string

This is an example of what type of sampling? -A professor asks the first 5 students who arrive to class to participate in a research study about young adult sleep patterns. A.Convenience B.Purposive Sampling C.Quota Sampling D.Referral /Snowball Sampling

A

This is an example of what type of sampling? -A teacher puts students' names in a hat and chooses without looking to get a sample of 33 students. A.Simple random sample B.Stratified random sample C.Cluster random sample D.None of the above

A

This is an example of what type of sampling? -Researchers study networks of drug users recruit three drug users and ask each of them to recruit another three research participants through their network. A.Convenience B.Purposive Sampling C.Quota Sampling D.Referral /Snowball Sampling

D

Inferential or descriptive? -Average age of everyone in this class (i.e., mean)

Descriptive

Inferential or descriptive? -The most popular college major (i.e., mode)

Descriptive

Used to organize and describe the characteristics of a particular data set

Descriptive statistics (We want to know information ABOUT a population)

What are the two major branches of statistics?

Descriptive statistics and inferential statistics

What type of variable? -Observations can take a value based on a count from a set of distinct whole values. A ______ variable cannot take the value of a fraction between one value and the next closest value. -Examples: the number of registered cars, number of business locations, and number of children in a family, all of which measured as whole units (i.e. 1, 2, 3 cars).

Discrete

What are the two types of numeric variables?

Discrete and continuous

Inferential or descriptive? -What is the most popular major among college students in Indiana?

Inferential (College students in Indiana is the population, but you can't get data from EVERY student in Indiana, so you choose a sample from 3 universities)

A sample is a subset of a population and used in....

Inferential Statistics (*Refugees* in the United States. You can't get information from ALL refugees in the United States, so you take a sample to model that population.)

________ are techniques that use the samples of populations to make generalizations about the populations from which the samples were drawn.

Inferential statistics

Differences between inferential and descriptive statistics

Inferential: -Is how we say something about a group when we haven't been able to test each group member. -Is more than just describing. It compares groups, tests hypothesis, and makes predictions. -When we compare, test, or predict the most popular major that we haven't examined directly. Descriptive: -When we illustrate or summarize data we already have. -Describe or summarize things that you definitely know. -Have a list of major of college students. With all this information, you can describe which major is the most popular major.

What type of sampling? - This is based on the intention or the purpose of study. Only those elements will be selected from the population which suits the best for the purpose of our study. -For Example: If we want to understand the thought process of the people who are interested in pursuing master's degree then the selection criteria would be "Are you interested for Masters in..?"

Purposive sampling

What type of sampling? -This type of sampling depends of some pre-set standard. It selects the representative sample from the population. Proportion of characteristics in sample should be same as population. Elements are selected until exact proportions of certain types of data is obtained or sufficient data in different categories is collected. -For example: If our population has 45% females and 55% males then our sample should reflect the same percentage of males and females.

Quota sampling

A ______ is a subset of a population

Sample

The process of selecting a sample is known as sampling. The number of elements in the sample is the...

Sample size

The process of selecting a sample is known as...

Sampling

A list of all the elements in the population from which the sample is drawn

Sampling frame

-Every element has an equal chance of getting selected to be the part sample. -A sampling frame is required for _______ (a list of all the elements in the population from which the sample is drawn)

Simple random sampling

What type of sampling? -Random selection of 20 students from class of 50 student. Each student has equal chance of getting selected.

Simple random sampling (SRS)

What type of cluster sampling? -Entire cluster is selected randomly for sampling.

Single stage

What are the two types of cluster sampling?

Single stage and two stage cluster sampling

What type of sampling? -This technique is used in the situations where the population is completely unknown and rare. -Researchers will take the help from the first element which we select for the population and ask him to recommend other elements who will fit the description of the sample needed. -As this referral technique goes on, the population size increases

Snowball/referral sampling

A set of tools and techniques used for describing, organizing, and interpreting information or data. -"Data analysis"

Statistics

What type of sampling? -Population is divided into subgroups according to some variable or variables (age, gender, ethnic origin, SES, diagnosis, geographic region, institution, or type of care) which are important to the study. Then the elements are randomly selected from each subgroup.

Stratified sampling

What SPSS variable? -May contain letters, numbers and other characters. You can't do calculations on ______ variables -even if they contain only numbers.

String (Zip codes and phone numbers, although composed of numbers, are typically considered string variables because their values cannot be used meaningfully in calculations.)

What type of sampling? -A random sampling process in which every kth (e.g. every 4th element) or member of the population is selected for the sample after a random start is determined. -All the elements are put together in a sequence first where each element has the equal chance of being selected.

Systematic sampling

What type of cluster sampling? -First we randomly select clusters and then from those selected clusters we randomly select elements for sampling

Two stage

For __________ sampling, you cannot generalize your results to an entire population with a high level of confidence

non-probability sampling

Is probability or non-probability sampling more convenient and less costly?

non-probability sampling

Probability or non-probability sampling? -Convenience sampling

non-probability sampling

Probability or non-probability sampling? -Purposive sampling

non-probability sampling

Probability or non-probability sampling? -Quota sampling

non-probability sampling

Probability or non-probability sampling? -Snowball/referral sampling

non-probability sampling