Types of Statistical Studies Math 075 Summer 2016

Population Vs. Sample We’d like to know about an entire population of individuals, but examining all of them is usually impractical, if not impossible. We settle for examining a smaller group of individuals—a sample— selected from the population.

Population Vs. Sample Sampling is a natural thing to do. Think about sampling something you are cooking—you taste (examine) a small part of what you’re cooking to get an idea about the dish as a whole.

Population or Sample Sample Sample Population A survey of 500 COC students. The GPA of every student at Crown High School. The height of every fifth person entering a grocery store. Sample Population Sample

Speed Dating You will create two equal lines facing each other. You will have one-minute to discuss and answer the question I tell you to answer I will call time and then call on a student or two to answer the question and discuss why. Move to the right Repeat 

Good Research Questions Criteria: The population The variable: What is being measured A numerical characteristic about the population related to the variable.

Let’s Practice: What is the average amount of time teachers spend outside of the school grading papers? What is the population? What is the is being measured? What is the numerical characteristic about the population related to the variable? Teachers Amount of time spent grading The average amount of time spent grading

Let’s Practice What is the average amount of time spent on social media? What is the population? What is the is being measured? What is the numerical characteristic about the population related to the variable? A population was not identified Time spent on social media The average amount of time spent on social media

Project #1: Three Truths and a Lie You will work on groups of 3 – 4 students Your group will be creating 9 good research questions and 3 not very good research questions (don’t make it to obvious though) These questions will go into a power point presentation that you will present to the class. Your goal is to get more points then the other teams.

Observational Study Vs. Experiment Observational study: Observes individuals and measures variables of interest. Experiment: Intentionally manipulates one variable in an attempt to cause and effect on another variable. The purpose to create a cause-and-effect relationship.

Observational Study or Experiment Does reducing screen brightness increase battery life in laptop computers? To find out, researchers obtained 30 new laptops of the same brand. They chose 15 of the computers at random and adjusted their screens to the brightest setting. The other 15 laptops screens were left at the default setting- moderate brightness. Researches then measure how long each machine’s battery lasted. Is this an observational study or experiment? Justify your answer. Experiment because the treatment was imposed on the laptops.

Observational Study or Experiment An educator wants to compare the effectiveness of computer software for teaching biology with that of a textbook presentation. She gives a biology pretest to each of a group of high school juniors, then randomly divides them into two groups. One group uses the computer, and the other studies the text. At the end of the year, she tests all students again and compares the increase in biology test scores in the two groups. . Is this an observational study or experiment? Justify your answer. Experiment because students were assigned randomly to the different teaching methods

Observational Study or Experiment One study of cell phones and the risk of brain cancer looked at a group of 469 people who have brain cancer. The investigators matched each cancer patient with a person of the same age, gender, and race who did not have brain cancer, then asked about the use of cell phones. Results “Our data suggest that the use of handheld cellular phones is not associated with the risk of brain cancer.” Is this an observational study or experiment? Justify your answer. Observational because the researchers did not assign people to either use or not use cell phones.

Observational Study or Experiment A study of child care enrolled 1364 infants and followed them through their sixth grade year in school. Later, the researcher published an article in which they stated that “the more time children spent in child care from birth to age four-and-a-half, the more adults tended to rate them, both at age four-and-a-half and kindergarten, as less likely to get along with others, as more assertive, as disobedient, and as aggressive. Is this an observational study or experiment? Justify your answer. Observational because children weren’t assigned to different amounts of child care.

Experiment Relationship between two variables Explanatory: The factor you are manipulating Response: The variable we are measuring

Explanatory and Response Does reducing screen brightness increase battery life in laptop computers? To find out, researchers obtained 30 new laptops of the same brand. They chose 15 of the computers at random and adjusted their screens to the brightest setting. The other 15 laptops screens were left at the default setting-moderate brightness. Researches then measure how long each machine’s battery lasted. Justify your answer. Explanatory: Screen brightness Response: The length of each battery lasted

Explanatory and Response An educator wants to compare the effectiveness of computer software for teaching biology with that of a textbook presentation. She gives a biology pretest to each of a group of high school juniors, then randomly divides them into two groups. One group uses the computer, and the other studies the text. At the end of the year, she tests all students again and compares the increase in biology test scores in the two groups. Justify your answer. Explanatory: Delivery method Response: The grades on the post test

Observational Study Provides evidence of a link between two variables. Confounding variables: Other factors that might influence the results

Confounding Variable A study of child care enrolled 1364 infants and followed them through their sixth grade year in school. Later, the researcher published an article in which they stated that “the more time children spent in child care from birth to age four-and-a-half, the more adults tended to rate them, both at age four-and-a-half and kindergarten, as less likely to get along with others, as more assertive, as disobedient, and as aggressive. Home-life Disposition What they area exposed to growing up

Confounding Variable One study of cell phones and the risk of brain cancer looked at a group of 469 people who have brain cancer. The investigators matched each cancer patient with a person of the same age, gender, and race who did not have brain cancer, then asked about the use of cell phones. Results “Our data suggest that the use of handheld cellular phones is not associated with the risk of brain cancer.” Environmental factors other than cell phones.

Exit Ticket What is the difference between a sample and population? What is the difference between an Observational Study and Experiment? What are the three criteria for a good research question. Choose one.