# How Science Works (HSW) & Math skills Flashcards

1
Q

Valid conclusions need……

A

Need:

• Large sample size SO representative
• Long study SO can allow…. / see effect of X
• Control used SO comparison can be made.
*Mean & SD SO significant differences can be determined.
2
Q

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

A
• Pain perception is subjective / pain threshold varies
• To ensure that differences (in pain detection) were (statistically) significant / differences not due to chance
• For (valid) comparison;
3
Q

Limitations:

You can only use the information provided.

A
• Small sample size, not representative;
• Only sampled males, females may respond differently to treatment;
• Only tested on …….. in a lab, in the wild, may obtain different pattern in data;
• Only tested on …….. species, might not be true for all species;
• No STATS test so differences could be due to chance;
• Data is SUBJECTIVE, some people may have lied
4
Q

Null hypothesis (How to write one)

A
• [x] will have no effect on [y]
• E.g. Temperature will have no effect on rate of reaction
• There will be no correlation between age and weight
• There will be no difference between the observed and expected ratio of 3:1 brown eyes to blue eyes
5
Q

Explain why a log scale is used to record the number of cells/bacteria.

A
• Large range/difference/increase in numbers;
• Accept reference to exponential (increase)
6
Q

In the UK in 2017, there were 805 000 deaths.

Cancer caused 29% of all deaths.

Throat cancer caused 4% of all deaths from cancer.

Calculate the mean number of people who died of throat cancer per month in 2017.

A

778

(805 000 x 0.29 x 0.04) / 12

7
Q

Information travels at 120 metres per second in neurones.

Calculate the time it would take for the information to travel 1.8 m along a neurone.

A

15 ms

(1.8/120) x 1000

8
Q

A ruler has an error of ± 1 mm.

An object’s length was 5.7 mm.

Calculate the % error of uncertainty.

to 2 DP

A

17.54 %

9
Q

What is the equation for uncertainty of a measurement?

A

Meauremement: (one interval / actual measurement) *100

10
Q

Calculate the percentage change in mass [grams]:

Mass before = 6.3 g

Mass after = 2.4 g

A

(Difference / Original) x 100

(3.9 / 6.3) *100

= 61.9 %

11
Q

Calculate the mean value:

8.4, 2.5, 4, 1.1, 8.5, 8.5, 7, 2.5, 7.9

A

8.4+2.5+4+1.1+8.5+8.5+7+2.5+7.9
________________________________________
9

= 5.6

12
Q

Which P value(s) shows a difference is significant.

a) P=0.06
b) P>0.05
c) P<0.05
d) P<0.50

A

c) P<0.05

The probability that the difference is due to a random chance event is less than 5%

13
Q

A scientist determined the volume of a plant cell and the volume of organelles it contained.

They found:

• the volume of a plant cell is 18 500 µm3
• the volume of all the mitochondria in a plant cell is 262.5 µm3
• the volume of all the mitochondria and all the chloroplasts in a plant cell is 46.1% of the volume of a plant cell.

Use this information to calculate the volume of all the chloroplasts in a plant cell.

A

8266 µm3

18 500 x 0.461 = 8528.5;

8528.5 - 262.5;

14
Q

Define Standard Deviation.

A

The spread of data around the mean

15
Q

Large SD bars indicate…….

A

A large range of variation in the data.
Less reliable mean value.

16
Q

Explain the advantage of showing the data using standard deviations rather than ranges.

A
1. SD is spread of data around the mean;

Accept: range is difference between highest and lowest values/extremes or range includes anomalies/outliers.

1. (SD) reduces effect of anomalies/ outliers;

Reject: (SD) removes anomalies/outliers.

1. (SD) can be used to determine if (difference in results is) significant/not significant/due to chance /not due to chance; or allows a STATS test to be performed to determine if differences are significant.
17
Q

Which stats test would you use if the data is categoric?

A

CHI SQUARED

18
Q

Which stats test would you use to see if there is a relationship between two variables?

A

Correlation coefficient
Spearman’s Rank

19
Q

Which stats test would you use to see if there is a difference between two means?

A

Student T test

20
Q

If Y = 16.56 find the value of x

y = 0.72x + 4

A

x= 17.4

21
Q

The scientists measured the percentage change in tumour volume.

Suggest why they recorded both percentage change and tumour volume.

A

Percentage change: To allow comparison as tumours may differ in volume/size
Tumour volume: (As) tumours may differ in length/width/shape OR
(As) volume is (best) indication of the number of cells in tumour;

22
Q

Drug X is delivered at a dosage of 3 ng Kg-1h-1 for 8 days into a patient.

1ng = 1 x10-9 g

Calculate the total mass in grams of drug X injected after 8 days into a patient with a body mass of 82 kg.

[2]

A

5x10-5;;

3 x (8x24) x 82 = 47232;

47232 / 1 000 000 000;

23
Q

The concentration of ATP in skeletal muscle is approximately
5 × 10–3 mmol g–1

During maximum exercise, ATP in skeletal muscle is used at a rate of approximately 3.7 mmol kg–1 s–1.

Calculate how long maximum exercise would last if ATP was not resynthesised.

A

1.35 or 1.4 seconds;;

5x10-3 mmol g-1 x 1000 (Unit conversion)

5/3.7 = 1.35 seconds

Concentration available: