Sure, let's go through each question step by step.
### 1.1 State the sample size of this investigation.
The sample size is the total number of rats across all groups. Here, we have 3 rats in Group A, 3 rats in Group B, and 3 rats in Group C. Therefore, the sample size is:
[tex]\[ 3 (Group A) + 3 (Group B) + 3 (Group C) = 9 \][/tex]
So, the sample size is:
[tex]\[ \boxed{9} \][/tex]
### 1.2 Calculate the average mass of (i), (ii) and (iii).
To calculate the average mass for each group, we add the masses of the three rats in each group and divide by 3.
#### (i) Group A
Masses: 320 g, 322 g, 322 g
Average Mass:
[tex]\[ \text{Average Mass} = \frac{320 + 322 + 322}{3} = \frac{964}{3} = 321.33 \, \text{g} \][/tex]
So, the average mass for (i) is:
[tex]\[ \boxed{321.33 \, \text{g}} \][/tex]
#### (ii) Group B
Masses: 305 g, 315 g, 308 g
Average Mass:
[tex]\[ \text{Average Mass} = \frac{305 + 315 + 308}{3} = \frac{928}{3} = 309.33 \, \text{g} \][/tex]
So, the average mass for (ii) is:
[tex]\[ \boxed{309.33 \, \text{g}} \][/tex]
#### (iii) Group C
Masses: 345 g, 338 g, 337 g
Average Mass:
[tex]\[ \text{Average Mass} = \frac{345 + 338 + 337}{3} = \frac{1020}{3} = 340.00 \, \text{g} \][/tex]
So, the average mass for (iii) is:
[tex]\[ \boxed{340.00 \, \text{g}} \][/tex]
### 1.3 Which group has the highest average:
#### a) Oxygen consumption
From the given data, the average oxygen consumption for each group is:
- Group A: 10 ml/kg/min
- Group B: 2.7 ml/kg/min
- Group C: (not given)
Among Group A and B, Group A has the highest average oxygen consumption of 10 ml/kg/min.
So, the group with the highest oxygen consumption is:
[tex]\[ \boxed{\text{Group A}} \][/tex]
#### b) Average mass after three weeks
From the averages calculated above:
- Group A: 321.33 g
- Group B: 309.33 g
- Group C: 340.00 g
The highest average mass after three weeks is 340.00 g, which is for Group C.
So, the group with the highest average mass is:
[tex]\[ \boxed{\text{Group C}} \][/tex]
### 1.4 What effect does an increase in thyroxin have on oxygen consumption?
An increase in thyroxin level increases oxygen consumption.
So, the effect is:
[tex]\[ \boxed{\text{increases oxygen consumption}} \][/tex]
### 1.5 Which group [tex]$(A, B,$[/tex] or [tex]$C)$[/tex] is the control in this investigation?
Typically, a control group is the one with a normal (or standard) diet and conditions. In this investigation, Group C can be inferred to be the control group based on standard conditions (average mass analysis).
So, the control group is:
[tex]\[ \boxed{\text{Group C}} \][/tex]
