general exam tips

Question 1

why do the standard deviations differ

Answer 1

different groups have different spreads of data around the mean

Question 2

what does it mean when the standard deviations overlap

Answer 2

-the data is not significant - so there is no significant difference in the values

Question 3

what does it mean when the standard deviations dont overlap

Answer 3

-the data is significant - there is a significant difference between the means

Question 4

estimate the value of the correlation coeffeicent of a postive correlation

Answer 4

-close to +1
-so between 0.5 and 0.99

Question 5

estimate the value of a negative correlation coefficient

Answer 5

-close to 0
-0 to 0.5

Question 6

sugegst some considerations that should have been taken into account to ensure that the study was reliable

Answer 6

-large sample size
-chose ppl randomly
-chose ppl with a range of ages
-equal number of males and females
-repeat readings/measurements

Question 7

why do the shapes/size in the image appear to be different comapred to each other and in real life

Answer 7

shape- tissue has been treated/killed/damaged
size-cut through different sections/planes

Question 8

patients recorded the intensity of pain, suggest two reasons why it was
important to use a statistically valid scale.

Answer 8

1. (Sensation of) pain is subjective
   OR
   Pain sensitivity/threshold/tolerance varies;
2. To ensure that differences (in pain detection)
   were (statistically) significant
   OR
   For (valid) comparison;

Question 9

Suggest what the scientist should do to ensure that he has removed all the water from
the sample.

Answer 9

1. Weigh and heat;
2. (Until) mass is constant;

Question 10

suggest one explanation for why the transmission reaction was less than 45 ms in trial 3

Answer 10

-student started to move her hand before the ruler was released
-ruler didnt fall vertically
-ruler stuck to skin
- student b held ruler to high

Question 11

in response to touch, nerve impulses can be transmitted at speeds of 76.2 m s-1
-suggest three reasons why, in this investigation, the estimated speed of student A’s impulse transmission was less than 76.2 ms-1

Answer 11

-synaptic transmission OR transmission at a neuromuscular junction
-time for muscle contraction
-time taken for (stretch-mediated) sodium ion channels to open
-student may have been distracted/concentrating
-time taken for coordination/comprehension (by the brain)

Question 12

if not asked for % of mitoitc index

Answer 12

do not times by 100
-just divide number of cells in mitosis by the total number of cells

Question 13

give reasons why bacteria/ other organisms are able to use human DNA to produce human proteins

Answer 13

-genetic code is universal
-mechanism of transcription is universal
-mechanism of translation is universal

Question 14

explain the importance of the marker gene

Answer 14

-shows that the gene has been taken up by the cells
-shows the transgenic/transformed cells
-allows detection of GM cells/organims

Question 15

the enhancer only stimulates the region M in a certain area
-suggests reasons for the importance of the enhancer being included in the DNA fragment transferred

Answer 15

-milk/protein is easy to extract from a goat
-extracting milk does not harm the goat
-if gene was in the blood could prevent/affect clotting
-could damage other cells