You decide to set a, the probability of a type 1 error, at 0.05.

(a) If the null hypothesis is true, what is the probability that you will reject it?

(b) What is the probability that T>1.0?

(c) What is the probability that T lies within 1.96 standard deviations of zero, if the null hypothesis is true?

(d) What is meant by a type 2 error?

If you now set a=0.01.

(e) What is the probability that T will lie within 1.96 standard deviations of zero?

(10 minutes)

Question 6.

Assume that you are testing the conjecture that adults living high in the Andes have red-cell 2,3 DPG concentrations that differ from those of people living at sea level. You measure red-cell 2,3 DPG levels in 50 adults from the Andes and 50 living at sea level.

(a) State an appropriate null hypothesis

(b) Define, in this context, a type I error

(c) Define, in this context, a type II error

(d) If you were asked by a statistical colleague what you wanted to use for an a value in testing your null hypothesis, what would he or she mean?

(e) If a statistical colleague, in testing the null hypothesis, told you he/she had set b=0.2, what additional information would you need before attaching some meaning to his/her statement?

[15 minutes]

Bill Barton is a 41 year old truck driver who previously worked independently but has recently taken a position with a large national transport business. His new company requires a medical examination as a prelude to joining the company superannuation scheme.

Bill is 1.70 m tall and 105 kg.

He says that his general health has been OK and he is not on any medication. He says that because of working irregular, long hours he gave up ten-pin bowling nights which used to be his main opportunity for exercise. "I never drink alcohol because of driving but I do get through a lot of soft drink in a day. I'm always thirsty. When I'm home I sometimes get up 3 or 4 times in a night to urinate". Apart from his obesity and blood pressure of 150/90, Bill's physical examination is within normal limits. The GP conducting the medical examination uses a dipstick to test a sample of Bill's urine (taken 3 hours after he ate breakfast). The urine test is positive for glucose.

Question 7.

(a) Outline the two hypotheses that you consider most likely to account for the presence of glucose in Mr Barton's urine. For each hypothesis, suggest the mechanisms leading to the presence of glucose in the urine.

[12 minutes]

(b) Identify aspects of the history or findings from the examination which provide support for, or weigh against, either or both of your hypotheses. Explain your reasoning.

[6 minutes]

Question 8.

Outline three laboratory tests that you would conduct with highest priority to confirm, eliminate or distinguish between your hypotheses, explaining your reasoning in each case.

[12 minutes]

The GP repeats the test on Mr Barton's urine with a combination test-strip that gives readings asfollows:

Analyte Result

Protein: negative

Glucose: positive

Ketones: below detection limit

Question 9.

For each of the analytes, protein, glucose and ketones (such as 3-hydroxybutyrate, acetoacetate), discuss

(a) whether it normally appears in the glomerular filtrate and why this is so.

(b) if relevant, what happens to the analyte as it passes through the nephron

(c) how the urine findings for Bill Barton, on their own, might be interpreted.

[12 minutes]

Measurements on the plasma samples from Bill Barton give the following results:

Reference Range

Glucose 12.1 mmol/L 3.0-5.5 mmol/L (fasting)

3-hydroxy butyrate 0.2 mmol/L below 0.3 mmol/L

The GP arranges for Bill to fast overnight then take a Glucose Tolerance Test. Blood samples are taken before, and at various times after, Bill consumes 75 g glucose in 300 ml of cold flavoured water. The values for plasma glucose and insulin levels are shown below.

Question 10

For a normal person, account for the changes in blood glucose levels occurring in the first 2 hours after the glucose load. Include in your answer an outline of the major controls and relevant metabolic events in :

• liver;

• adipose tissue; and

• muscle

[16 minutes]

Question 11

Discuss the differences from normal in Bill Barton's response to the glucose load. Suggest how metabolic events are altered from the normal situation described in Question 10. In your answer summarise what is now your most favoured hypothesis to account for Bill's high glucose levels in plasma and urine.

[12 minutes]