MAT5212: Biostatistics - Vitamin B12 Levels - The Fasted and Non-Fasted Groups - Science Assignment Help

Assignment Task:

QUESTION 1 

Vitamin B12 is an essential coenzyme. It plays a key role in neurological function and red blood cell development. Vitamin B12 deficiency can present with a wide variety of symptoms, including fatigue, dizziness, mood changes, and disturbed vision. As Vitamin B12 is found almost exclusively in animal-based food sources, plant-based diets can result in deficiency. Therefore, it is important for people who follow plant-based diets to regularly check their Vitamin B12 levels. A recent study showed that the requirement for fasting prior to the Vitamin B12 blood test was not standardised across clinical sites. To assess whether fasting had an effect on the observed Vitamin B12 blood levels, the researchers divided patients into two different groups (Fasted and Non-Fasted) and then compared their measured Vitamin B12 levels. The data can be found in your excel file in the ‘VitB12’ sheet.

(a) Calculate the sample mean and sample standard deviation of the measured Vitamin B12 levels for the Fasted and Non-Fasted groups. [2 marks]

(b) Perform the appropriate test at the 5% level of significance to determine whether there is a significant difference in the mean measured Vitamin B12 levels between the Fasted and NonFasted groups. State all assumptions associated with you chosen test. [8 marks]

(c) Find the 95% confidence interval for the true mean difference in measured Vitamin B12 between the Fasted and Non-Fasted groups. [2 marks]

(d) Does your 95% confidence interval in part (c) support your conclusion in (b)? If so, explain how. [2 marks]  

QUESTION 2

Phosphorous, an element found in soil, is necessary for adequate plant growth. Forest fires are known to change the composition of certain soil elements. To determine whether forest fires affect the soil phosphorous levels, a research group measured surface soil phosphorous levels at the exact same forest sites just before and just after a forest fire. The data for this question can be found in the ‘ForestFire’ worksheet of your excel file.

(a) What is the appropriate test for the study? Explain your reasoning. [2 marks]

(b) Using SPSS, test your hypothesis at the 5% level of significance. Take care to include every step of the hypothesis test, including any assumptions made and conclusions derived. Attach all relevant SPSS output to support your answers. [8 marks]

(c) From your SPSS output in part (b), what is the 95% confidence interval for the true mean difference in soil phosphorous levels? [

QUESTION 3

D-Dimer is a small protein fragment found in blood that is indicative of blood clotting. D-dimer concentration above a threshold of 500 ng/ml is used to diagnose venous thromboembolism (VTE). It is suspected that in healthy pregnancy D-Dimer levels naturally increase above this threshold, thereby leading to false positive VTE test results. In order to assess how D-Dimer changes during healthy pregnancy, 30 healthy pregnant women were recruited, and their D-Dimer concentrations were measured during each of the 3 pregnancy trimesters. The aim of the study is to determine if DDimer concentrations change significantly across the three trimesters of pregnancy. The data for this question can be found in the ‘D-Dimer’ sheet of your excel file.

(a) Use an appropriate test to manually determine whether there is a difference in the mean DDimer levels for pregnant women in their 1st, 2nd, and 3rd trimester. If there is a difference, perform the Bonferroni test to determine which group means are different. [17 marks]

(b) What are the assumptions associated with your chosen test in part (a)? Use SPSS to verify them. Do these assumptions hold? Attach all relevant SPSS output to support your answers. If the assumptions do not hold state way(s) to deal with this. 

QUESTION 4

Sustainability is important to the fishing industry. In efforts to improve sustainability of rock lobsters, commercial hatcheries are now being used. To optimise efficiency in culturing practices, it is important to understand factors that affect incubation time (i.e. time it takes for eggs to hatch). One possible factor is incubation temperature. Data were collected on the hatching times (in days) of rock lobster eggs incubated at four different temperatures 20°C, 25°C, 30°C, 35°C. Evaluate whether different incubation temperatures have any significant effect on hatching time. The data for this question can be found in the ‘Lobster’ sheet of your excel file.

(a) Use SPSS to evaluate whether temperature affects the mean incubation time for rock lobsters. Use a 5% level of significance for your test. If there is any difference, determine which temperatures are significantly different from each other using the Bonferroni test. Take care to include every step of the hypothesis test and explanation on how the conclusions were derived. Attach all relevant SPSS output to support your answers. Note: You do not need to include the test of the assumptions here as that is to be done in part (b). 

(b) What are the assumptions associated with your chosen test in part (a)? Use SPSS to verify them. Do these assumptions hold? Attach all relevant SPSS output to support your answers. 

QUESTION 5

What assumption do all of the above hypothesis tests share? Should such assumption not be met, how can it be overcome?

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