Question

name: dejoux floyd date: 9/ elements of experimentation identifying the flaws in experimental design instructions: for each of the experimental methods below, there is at least one flaw in design. identify this flaw (or flaws) and explain what the experimenter might be able to do differently. 1. ms. smith wants to see which fertilizer is best for her plant. she believes that fertilizer c will allow her plant to grow the fastest. she has three different fertilizers to test. she uses three plants: the first plant gets fertilizer a and 5ml of water, the second plant gets fertilizer b and 10ml of water, and the third plant gets fertilizer c and 15ml of water. list the flaw(s): what should the experimenter do differently? 2. a nutritionist has all of her clients drink only water (no other types of beverages). she believes that if she instructs them to replace all of their beverages with lemon water instead, they will lose more weight. she instructs her female clients to replace all beverages with lemon water and has her male clients continue to drink only water as usual. list the flaw(s): what should the experimenter do differently?

Explanation:

1. Flaw: In Ms. Smith's plant - fertilizer experiment, there are multiple variables. The amount of water is not controlled (5ml, 10ml, 15ml for the three plants respectively), so it's impossible to determine if differences in plant growth are due to the fertilizer or the water amount.

• What to do differently: Use the same amount of water for each plant while testing the fertilizers.

1. Flaw: In the nutritionist's experiment, there are two confounding variables. One is gender (male vs. female clients), and the other is the type of beverage (lemon - water vs. regular water). It's unclear whether any weight - loss differences are due to the beverage type or gender.

• What to do differently: Either have all clients (regardless of gender) drink only water or have all clients (regardless of gender) drink lemon - water, or control for gender by having equal numbers of male and female clients in both the lemon - water and regular - water groups and controlling other variables like diet and exercise.

Answer:

1. Flaw: Uncontrolled variable (amount of water). What to do differently: Use equal amounts of water for each plant.
2. Flaw: Confounding variables (gender and beverage type). What to do differently: Control for gender and beverage type more effectively (e.g., same gender groups for both beverage types or all clients on one beverage type).