Question

read the experimental set-up below. 1) identify what was done incorrectly in each section of the experiment 2) correct what was done incorrectly.

1. an experiment is designed to see if mosquitoes choose prey based on blood type. you choose 3 blood types to investigate.

h₀: blood type o+ will be the preferred food source
h₁: blood type a+ will be the preferred food source
h₂: blood type b+ will be the preferred food source
image of three droplets: o+, a+, b+
next, individuals are chosen who will participate in the experiment. each group has 3 individuals who are approximately the same age, height, weight, and blood type.
images: group a (o+ with three male figures), group b (a+ with three female figures), group c (b+ with three female figures)
lastly, the total number of bites per group over the course of one hour were recorded to determine if there is a blood type preference among the mosquitoes being studied. group b had the highest number of bites. the researchers concluded that their hypothesis was correct.

Explanation:

Part 1: Hypothesis Section

Incorrect Action:

The null hypothesis (\(H_0\)) is incorrectly formulated as a directional prediction (claiming O+ is preferred) instead of a statement of no difference. The alternative hypotheses (\(H_1, H_2\)) are also misdefined (they should not be multiple directional predictions but a general statement of a difference, or the null should be no preference, and the alternative should be that there is a preference or a specific preference).

Correction:

• \(H_0\): Mosquitoes show no preference for any of the three blood types (O+, A+, B+).
• \(H_1\): Mosquitoes prefer one (or more) of the blood types (O+, A+, B+) over the others.

Part 2: Participant Selection Section

Incorrect Action:

Participants in different groups have different genders (Group A: male; Groups B, C: female) and the same blood type within each group (which is redundant, as the experiment is about blood type preference—blood type should vary, and other variables like gender should be controlled).

Correction:

• Ensure all participants (across all groups) have the same gender (or balance gender evenly across groups) to control for gender as a confounding variable.
• Each group should consist of individuals with the target blood type (e.g., Group A: O+, Group B: A+, Group C: B+), and all other variables (age, height, weight, gender) should be held constant across groups.

Part 3: Conclusion Section

Incorrect Action:

The researchers concluded their hypothesis was “correct” without specifying which hypothesis (they had three alternative hypotheses, and Group B (A+) had the highest bites, but their \(H_1\) was about A+ being preferred—however, the initial hypothesis setup was flawed). Additionally, the conclusion does not account for whether the result is statistically significant (just counting bites is insufficient to confirm a hypothesis; statistical testing is needed).

Correction:

• First, clarify the hypotheses (as corrected above). If the alternative hypothesis is that mosquitoes prefer a specific blood type (e.g., A+), compare the bite counts statistically (e.g., using a one-way ANOVA or chi-square test) to determine if the difference in bites is significant.
• If Group B (A+) has significantly more bites, conclude that there is evidence to support the alternative hypothesis (that A+ is preferred) and reject the null hypothesis. If not, fail to reject the null.

Summary of Corrections:

1. Hypotheses: Redefine \(H_0\) as “no preference” and \(H_1\) as “preference for a blood type.”
2. Participants: Standardize gender (and other variables) across groups; ensure each group has the target blood type.
3. Conclusion: Use statistical testing to determine significance before concluding hypothesis support.

Answer:

Part 1: Hypothesis Section

Incorrect Action:

The null hypothesis (\(H_0\)) is incorrectly formulated as a directional prediction (claiming O+ is preferred) instead of a statement of no difference. The alternative hypotheses (\(H_1, H_2\)) are also misdefined (they should not be multiple directional predictions but a general statement of a difference, or the null should be no preference, and the alternative should be that there is a preference or a specific preference).

Correction:

• \(H_0\): Mosquitoes show no preference for any of the three blood types (O+, A+, B+).
• \(H_1\): Mosquitoes prefer one (or more) of the blood types (O+, A+, B+) over the others.

Part 2: Participant Selection Section

Incorrect Action:

Participants in different groups have different genders (Group A: male; Groups B, C: female) and the same blood type within each group (which is redundant, as the experiment is about blood type preference—blood type should vary, and other variables like gender should be controlled).

Correction:

• Ensure all participants (across all groups) have the same gender (or balance gender evenly across groups) to control for gender as a confounding variable.
• Each group should consist of individuals with the target blood type (e.g., Group A: O+, Group B: A+, Group C: B+), and all other variables (age, height, weight, gender) should be held constant across groups.

Part 3: Conclusion Section

Incorrect Action:

The researchers concluded their hypothesis was “correct” without specifying which hypothesis (they had three alternative hypotheses, and Group B (A+) had the highest bites, but their \(H_1\) was about A+ being preferred—however, the initial hypothesis setup was flawed). Additionally, the conclusion does not account for whether the result is statistically significant (just counting bites is insufficient to confirm a hypothesis; statistical testing is needed).

Correction:

• First, clarify the hypotheses (as corrected above). If the alternative hypothesis is that mosquitoes prefer a specific blood type (e.g., A+), compare the bite counts statistically (e.g., using a one-way ANOVA or chi-square test) to determine if the difference in bites is significant.
• If Group B (A+) has significantly more bites, conclude that there is evidence to support the alternative hypothesis (that A+ is preferred) and reject the null hypothesis. If not, fail to reject the null.

Summary of Corrections:

1. Hypotheses: Redefine \(H_0\) as “no preference” and \(H_1\) as “preference for a blood type.”
2. Participants: Standardize gender (and other variables) across groups; ensure each group has the target blood type.
3. Conclusion: Use statistical testing to determine significance before concluding hypothesis support.