1-3: Data collection and sampling techniques Note: This PowerPoint is only a summary and your main source should be the book.

Data collection Surveys Telephone Mail questionnaire Personal interviews Observational and Experimental Studies 1-3:Data collection and sampling techniques Note: This PowerPoint is only a summary and your main source should be the book.

Some Sampling Techniques Random sampling Systematic sampling Stratified sampling Cluster sampling To obtain samples that are unbiased,statisticians use four methods of sampling : Note: This PowerPoint is only a summary and your main source should be the book.

1- Random Sampling :are selected by using chance methods or random numbers. For example: Select random sample of 15 subjects out of 85 subjects Note: This PowerPoint is only a summary and your main source should be the book. sampling techniques:

A: 12, 27, 75, 95,62, 57, 13, 31, 06, 16, 49, 46, 71, 53, 41, 02 Note: This PowerPoint is only a summary and your main source should be the book.

For example:  There are 50 students in your class. N=50  You want a sample of 10. n=10  You have a class listing in alphabetical order. 5  Divide 50 by 10, you will get 5. K=N/n= 50/10=5 15  Randomly select any number between 1 and 5. That is your starting number. From there select every 5 th name until you reach the last one. 2- Systematic Sampling : are obtained by numbering each value in the population and then selecting the kth value. Note: This PowerPoint is only a summary and your main source should be the book. sampling techniques:

Note: This PowerPoint is only a summary and your main source should be the book.

sampling techniques: for example: A researcher select a random sample from each gender to check their blood pressure. 3-Stratified samples: are selected by dividing the population into groups (strata) according to some characteristic and then taking samples from each group.

4-Cluster samples are selected by dividing the population into groups and then taking samples of the groups.such as geographic area or schools in a large school district. For example : In a large school district,all teachers from two building are interviewed to determine whether they believe the students have less homework to do now than in previous years. Randomly selected 2 clusters Population divided into 4 clusters Randomly sampling techniques:

Summary of sampling techniques 1-Random : random number generator. 2-Systematic :every kth subject. 3-Stratified :divide population into group called “strata”. 4-Cluster :use intact groups. 5-Convenient :mall surveys. Note: This PowerPoint is only a summary and your main source should be the book.

1-4: Observational and Experimental Studies

For example:” if a researcher records how many students are wearing glasses in the Science building over a period of time “. Observational Study: The researcher merely observes what is happening or what has happened in the past and tries to draw conclusions based on these observations. Note: This PowerPoint is only a summary and your main source should be the book.

the researcher manipulates one of the variables and tries to determine how the manipulation influences other variables. Experimental Studies: for Example: 1- Patients were randomly assigned to two groups:one group was given drug A and the other group was given drug B to determine if the drug has an effect on patient’s blood pressure. 2-An Instructor has Three Teaching methods,he wants to apply a best method by seeing students grades. Note: This PowerPoint is only a summary and your main source should be the book.

 In a true experimental study, the subjects should be assigned to groups randomly. If this is not possible and a researcher uses intact groups, then he is performing a quasi-experimental study. Note: This PowerPoint is only a summary and your main source should be the book.

Experimental studies usually include two types of variable or The Independent variable or Explanatory variable is the one that is being manipulated by the researcher. The Dependent variable or Outcome variable is the resultant variable. Note: This PowerPoint is only a summary and your main source should be the book.

For example: 1 - Patients were randomly assigned to two groups:one group was given drug A and the other group was given drug B to determine if the drug has an effect on patient’s blood pressure. Independent Variable Dependent Variabe Drug A,Drug B Blood pressure Note: Statistical studies usually include one or more independent variables and one dependent variable. Note: This PowerPoint is only a summary and your main source should be the book.

A confounding variable is the variable that influences the dependent or outcome variable but cannot be separated from the independent variable. For Example :subjects on exercise program may improve their diet and perhaps that improve their health in other ways not due to exercise alone. Then diet becomes confounding variable. influence Exercise Weight Diet confounding Note: This PowerPoint is only a summary and your main source should be the book.

Uses and Missuses of statistics 1-5: Uses and Missuses of statistics Note: This PowerPoint is only a summary and your main source should be the book.

1- Suspect sample 2- Ambiguous Averages 3- changing Subject 4-Detached Statistic 5-Misleading Graphs 6- Faulty Survey Question 1-5: Uses and Missuses of statistics Note: This PowerPoint is only a summary and your main source should be the book.

1-5: Uses and Missuses of statistics  small samples  convenience sample  volunteer sample 1- Suspect sample: For example:” if 4 doctors were surveyed from 100 doctors”. Note: This PowerPoint is only a summary and your main source should be the book.

measures that are loosely called averages are the mean, median, mode and midrange. People who know this can without lying, select one of them to support their position. 2- Ambiguous Averages 1-5: Uses and Missuses of statistics Note: This PowerPoint is only a summary and your main source should be the book.

can occur when different values are used to represent the same data. 1-5: Uses and Missuses of statistics 3- changing Subject For example: if one political candidate say “ I will increase salaries a mere 3%” And another one say “I will increase salaries a whapping 6,000,000 $” And 3% =6,000,000 Note: This PowerPoint is only a summary and your main source should be the book.

it is the one in which no comparison is made. 4-Detached Statistic For example, one may say that “Our cookies has one- third fewer calories” Here, fewer than what? 1-5: Uses and Missuses of statistics Note: This PowerPoint is only a summary and your main source should be the book.

Usage of words such as may, suggest or some that imply connections but there is no guarantee 1-5: Uses and Missuses of statistics 5-Implied connection For example:” Eating fish may help to reduce your cholesterol”. may Some people Might help some Note: This PowerPoint is only a summary and your main source should be the book.

if graphs are drawn inappropriately, they can misrepresent the data and lead to false conclusions. 1-5: Uses and Missuses of statistics 6-Misleading Graphs 7- Faulty Survey Question should be sure that the questions are properly written since the way questions are phrased can influence the way people answer them. Note: This PowerPoint is only a summary and your main source should be the book.