Sampling Methods
A sales representative surveys her client base of 47 companies. She has 47 business cards, and decides to drop them all in a small box, shake them and reach and picl 5 cards.
Simple random sampling
A professor samples 100 students and measures their mood after watching either a documentary on climate change, or Happy Feet 2. What is the observational unit?
A student
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 increased their screens to the brightest setting. The other 15 of the computers were left at the default setting.
Experimental
Researchers design an experiment where tasters will rate the color and flavor of French fries from several groups of potatoes. The potatoes are either freshly picked, stored for a month at room temp, or stored for a month refrigerated. What is the experimental unit?
Potatoes (can be worded a few different ways)
The percentage you have to get on the first exam to skip SLA (Tuesday / Thursday) sessions
82%
A bank wishes to survey its customers. The decision is made to randomly pick 10 customers who just have banking accounts, 10 customers who just have savings accounts, and 10 who have both.
Stratified sampling
A pharmaceutical company is testing a new drug for blood pressure. They find that the experimental group had a lower blood pressure than their control group. What is the response variable?
Blood pressure
I put on a ghillie suit and hide in the arboretum, to attempt to collect qualitative data on what kind of conversations people are having in the arboretum.
Observational
Few people want discolored French fries. Potatoes are kept refrigerated before being cut into French fries to prevent spoiling and preserve flavors. Unfortunately, immediate processing of cold potatoes causes discoloring due to complex chemical reactions. The potatoes must therefore be brought to room temperature before processing.
Researchers design an experiment where tasters will rate the color and flavor of French fries from several groups of potatoes. The potatoes are either freshly picked, stored for a month at room temp, or stored for a month refrigerated. What is the treatment?
Storage method (again, wording can be different)
There is an infamous problem called the Monty Hall problem. In the original gameshow, there are three doors to choose from, one having the prize behind it.
You get two tries to pick a door. After you pick your first door, one of the other doors, an incorrect door (the gag prize, a goat, not the real prize door) is revealed.
So there are now two doors remaining. The door you originally picked, and the last door remaining. You must choose to switch doors, or stay with your first door. If you switched doors, what is the percent likelihood that you picked the prize-winning door?
66%
A factory produces 900 cans of Monster Energy drinks every hour. Every 100th can is selected for product testing.
Systematic sampling
A toy company that sells troll dolls is curious on whether more dolls will be bought if their irises are colors other than brown. They track sales revenue on their (control) brown-eyed troll dolls, red-eyed troll dolls, and magenta-eyed troll dolls. How many levels are there?
Three
I manifested that I would find stumble across a cool bag at the thrift store. Oh my glob, a cool bag! Manifesting works wonders.
Anecdote
Few people want discolored French fries. Potatoes are kept refrigerated before being cut into French fries to prevent spoiling and preserve flavors. Unfortunately, immediate processing of cold potatoes causes discoloring due to complex chemical reactions. The potatoes must therefore be brought to room temperature before processing.
Researchers design an experiment where tasters will rate the color and flavor of French fries from several groups of potatoes. The potatoes are either freshly picked, stored for a month at room temp, or stored for a month refrigerated. What is the response?
Color and flavor
Name 3 objects in Professor Daniel's story for remembering things
Door, snail, rock (sheesh, I don't even remember!)
You wish to survey people who have brought in their cars for service during the -past month. You decide to pick a random sample of gas stations in the city and then survey all the customers from those who had work done in the past month.
Cluster sampling
A toy company that sells troll dolls is curious on whether more dolls will be bought if their irises are colors other than brown. They track sales revenue on their (control) brown-eyed troll dolls, red-eyed troll dolls, and magenta-eyed troll dolls. What is the factor?
The eyes of troll dolls / troll dolls
Does eating dinner with their families improve students' academic performance? According to the ABC News Article, "Teenagers who eat with their families at least five times a week are more likely to get better grades in school." This finding was based on a sample survey conducted by researchers at Columbia University.
Observational
Control groups are used in experiments in order to
Control the effects of outside variables on the outcome
I have nine plants, and I want to measure their growth daily in millimeters. I sample nine different plants every day for 3 months. Assuming I did not measure any one of them incorrectly (no measurement error), how much will my sample data vary from the actual population data?
None; 0
Researchers are curious if GPA is related to extracurriculars for college students. They sample 100 Economics majors, 100 English majors, 250 Communications majors, and 300 Business majors.
Stratified sampling
Randomizing means...
(Not random assignment! Different concept)
This type of study can reach a conclusion of cause and effect
Experimental
I have nine pots of plants that are dying (most of them have more than 1 plant in them, which is why they are dying). I want to try 2 new fertilizers. I administer 3 pots of plants with Fertilizer 1, 3 with Fertilizer 2, and 3 I do nothing with. How many experimental units are there?
Nine
A new headache remedy was given to a group of 25 students who had headaches. Four hours after the new remedy, 20 of the subjects reported that their headaches had disappeared. From this you can conclude
Nothing