ENV 250 Module Six Homework: The Importance of Randomization and Blinding
Randomization is a method used in experiments and scientific research to assist researchers in sampling and assigning sample groups in their studies. Random number charts and online random number generators are methods that can be used to accomplish this. Using your assigned readings and the linked resources below, answer the following questions and create randomization schemes for each scenario.
What is the purpose of randomization and blinding in research studies?
Create a random number assignment for 9 units (numbered one through nine) using the online random number chart. Start on row 25, column 30 and skip any repeats. To do this, go to page 1 of the Table of Random Digits, look to the left most column and scroll down until you see the number 00025. Note that columns run vertical (up and down) while rows run horizontal (side to side). Starting at number 6 (column 1 of row 00025), count across the row until you reach column 30 (this will be the last number of the sixth column grouping) – you should land on a number 9). Use this as your starting point. To create the random number sequence, read across the columns and rows as if you are reading a book and record the last number of each column grouping until you have obtained all 9 numbers. (Hint: Your first number should be 9, the second number 4, the third number 3, and so on. Do not include the row numbers in your sequence counts (e.g. do not include the 6 from 00026, the 7 from 00027, etc.)).
Grace is researching the effect of selenium on zebrafish by exposing the fish to varying levels of selenium. She has one control group and four treatment groups. Each group consists of five aquariums that contain one fish each, for a total of 25 fish used in the study. Use the online random number generator to create a randomization scheme for Grace’s study. This should generate a randomized list depicting which aquarium each fish (1 – 25) will be placed in.
Darius is conducting research on the effect acid rain has on aquatic life, using rainbow trout as his test organism. His study will consist of a control and two treatment groups. Each group contains three individual fish, for a total of nine fish. In all, there will be three groups, each with three fish. Using an online random number generator, create a random number scheme showing which group each individual will be placed (Group 1 (Control), Group 2 (Treatment 1), or Group 3 (Treatment 2)). Enter each group label into the Treatment labels table. Next, enter the number of subjects per block (this will be the total number of groups used in the study) and the number of blocks (this will be the number of fish per group). This should generate a randomized list depicting which group each fish (1 – 9) will be placed in.
Zahra is conducting research on how simazine affects frog survivorship. She has one control group and four treatment groups. Each group consists of three aquariums containing two frogs. If each group consists of 3 aquariums and there are a total of 5 groups, there should be a total of 15 aquariums used (numbered 1 – 15). If two frogs are placed in each aquarium, a total of 30 frogs will be needed. Using an online random number generator, create a random number scheme for placing each frog into an aquarium. Enter the aquarium numbers (Aquarium 1, Aquarium 2, …, Aquarium 15) into the Treatment labels table. Next, enter the number of subjects per block (this will be the total number of aquariums used in the study) and the number of blocks (this will be the total number of frogs placed in each aquarium). This should generate a randomized list depicting which aquarium each frog (1 – 30) will be placed in.
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