Processing Data

Question 1

How do you summarise data?

Answer 1

Find the mean and range.

Question 2

What should you not include in range and mean?

Answer 2

Anomalous results.

Question 3

What are descriptive statistics? give examples.

Answer 3

Describe patterns in data.

Mean, range and standard deviation.

Question 4

Why is the standard deviation better than the range?

Answer 4

It tells you how values are spread out about the mean rather than just the total spread of data.

Question 5

What does a small standard deviation mean?

Answer 5

It means the repeated results are similar and close to the mean.
More precise/accurate.

Question 6

Why is calculating %’s good?

Answer 6

Helps you to compare amounts from samples of different sizes.

Question 7

EXAMPLE.

In a DNA molecule containing 3000 bases, 900 of the bases are cytosine. What percentage are cytosine?

Answer 7

Divide 900 by 3000 = 0.30.

Multiply 0.30 by 100 = 30%

Question 8

What is the formula for % change?

Answer 8

Percentage change = final value - original value divided by original value times by 100.
Positive value = increase.
Negative value = decrease.

Question 9

Why is calculating % change good?

Answer 9

Helps to quantify how much something has changed.

Question 10

EXAMPLE.
A person’s blood glucose concentration was 4.2 mmol dm-3 before a meal and 2 hours after the meal it was 6.5 mmol dm-3.
Calculate the 5 change.

Answer 10

6.5 - 4.2 divided by 4.2 times 100 = 55%

The person’s blood glucose was 55% higher after the meal.

Question 11

Why can ratios be used?

Answer 11

To compare different types of quantities.

Question 12

EXAMPLE.

Write the ratio 28 : 36 in the form X : 1.

Answer 12

Divide both sides by 36.
28 divided by 36 = 0.78.
36 divided by 36 = 1
So the ratio is 0.78 : 1

Question 13

What is the first significant figure?

Answer 13

The first digit which isn’t a zero.

The 2nd, 3rd and 4th significant figures carry on immediately after the first even if they’re zeroes.

Question 14

EXAMPLE.

Round 0.6874976 to 2 s.f and 3 s.f.

Answer 14

0. 69 2s.f

0. 687 3s.f

Question 15

What happens if the calculation involves numbers to different significant figures.

Answer 15

Always give your answer to the lowest number of significant figures used in the calculation.
This is because fewer digits a measurement has the less accurate it is. So your answer can only be as accurate as the least accurate measurement in calculation.

Question 16

How can you deal with very large or very small numbers?

Answer 16

Convert it into standard form.

Question 17

How do you change very big/slow answers to standard form?

Answer 17

Move the decimal point left/right.
The number of times the decimal point moves is represented by a power of 10.
Big number = positive. Small numbers = negative.

Question 18

EXAMPLE.

Write 16,600 in standard form.

Answer 18

Move decimal point to give smallest number between 1 and 10.
Count the number of places the decimal point has moved.
It has moved 4 places to the left.
As its moved to the left the power is positive.
1.65 x 10(4)

Question 19

TIME.
How do you get from seconds to minutes.
And then minutes to hours.

Answer 19

Seconds to minutes DIVIDE by 60.
Minutes to seconds MULTIPLY by 60.
Minutes to hours DIVIDE by 60.
Hours to minutes MULTIPLY by 60.

Question 20

LENGTH.
How do you get from nanometres to micrometres
And then micrometres to millimetres.

Answer 20

Nanometres to micrometres DIVIDE by 1000.
Micrometres to nanometres MULTIPLY by 1000.
Micrometres to millimetres DIVIDE by 1000.
Millimetres to micrometres MULTIPLY by 1000.

Question 21

VOLUME.
How do you get from Centimetres cubed to decimetres cubed.
And then decimetres cubed to metres cubed.

Answer 21

Centimetres cubed to decimetres cubed DIVIDE by 1000.
Decimetres cubed to centimetres MULTIPLY by 1000.
Decimetres to metres cubed DIVIDE by 1000.
Metres cubed to decimetres MULTIPLY by 1000.

Question 22

Order from smaller to biggest.
Minutes.
Seconds.
Hours.

Answer 22

Seconds.
Minutes.
Hours.

Question 23

Order from smaller to biggest.
Millimetres.
Nanometres.
Micrometres.

Answer 23

Nanometres.
Micrometeres.
Millimetres.

Question 24

Order from smaller to biggest.
Metres cubed.
Decimetres cubed.
Centimetres cubed.

Answer 24

Centimetres cubed.
Decimetres cubed.
Metres cubed.

Question 25

EXAMPLE.
10cm3 of glucose solution is needed to create a dilution series.
What is the volume of glucose solution needed in dm3?

Answer 25

There are 1000 cm3 in one dm3, so you need to divide by 1000.
10 cm3 divide by 1000 = 0.01 dm3.

Question 26

Why are statistical tests good?

Answer 26

Means you can be more confident in your conclusion.

Question 27

Before you do a stat test what do you need to come up with?

Answer 27

A null hypothesis.
They states there is no significant relationship/difference between the things you’re investigating.
Collect data to try disprove null hypothesis.

Question 28

Students t-test.

Answer 28

2 sets of data you want to compare.
It tests if there is a significant difference in the means of 2 data sets.
Value obtained is compared to a critical value, which determines whether your result was due to chance or not.
If the value from test is higher than critical value at a probability of 5% or less then you can be 95% confident that the difference is significant and not due to chance - reject null.

Question 29

Chi-Squared.

Answer 29

Used when you have categorical data and you want to know whether your observed results are statistically different from expected results.
Compare your results to critical value.
If your result is larger than critical value at P = 0.05 you can be 95% confident the difference is significant.

Question 30

Correlation Coefficient.

Answer 30

Allows you to work out the degree to which 2 sets of data are correlated.
1 = strong positive correlation.
0 = no correlation.
-1 = strong negative correlation.
Compare your result to critical value to see if its significant or not.

Question 31

>

Answer 31

greater than.

Question 32

> >

Answer 32

much greater than.

Answer 33

less than.

Question 34

«

Answer 34

much less than.