Development Of Practical Skills :)

Question 1

Precise results describe

Answer 1

Don’t vary much from mean. Precision reduced by random error (unpredictable way in which all measurements vary)

Question 2

Repeatable means?

Answer 2

Repeatable means if same person repeats the same experiment using same method and equipment they will get the same result

Question 3

Reproducible means?

Answer 3

If someone different does the experiment using a slightly different method or piece of equipment the results will still be the same

Question 4

Valid results describe

Answer 4

Answer original question

To get valid results you need to control all variables to make sure you’re only testing the thing you want to

Question 5

Accurate results describe

Answer 5

Really close to true answer

Human interpretation of a measurement e.g.determining a colour change can reduce accuracy of results

Question 6

A good experiment gives results that are?

Answer 6

Precise
Repeatable and reproducible
Valid
Accurate

Question 7

How many variables should be changed at a time?

Answer 7

Only one
Variables are quantities that have the potential to change e.g. pH in an experiment that you can usually change one variable and measure its effect on another variable

Question 8

What’s the independent variable?

Answer 8

The variable you change

Question 9

What’s the dependent variable?

Answer 9

The variable you measure

Question 10

What should happen to all the other variables?

Answer 10

They should be controlled when you’re investigating a variable you need to keep everything else that could affect it constant meaning you can be sure that only your independent variable is affecting the thing you’re measuring (dependent variable)

Question 11

What else should be used?

Answer 11

Negative control
Used to check only the independent variable is affecting the dependent variable. Negative controls aren’t expected to have any effect in the experiment

Question 12

What should happen to the experiment?

Answer 12

Repeated at least three times and a mean should be calculated
Reducing effect of random error on your experiment making your results more precise. Doing repeats and getting similar results each time also shows data is repeatable and makes it more likely to be reproducible

Question 13

Example : investigating the effect of light intensity on rate of photosynthesis of Canadian pondweed?

Answer 13

Light intensity is the independent variable
Rate of photosynthesis is the dependent variable
pH, temperature and time pondered is left should stay the same (quantities recorded to allow someone else to reproduce experiment)
Repeated at least 3 times for each light intensity
Negative control of one in the dark so no photosynthesis should occur

Question 14

When planning an experiment what do you need to decide?

Answer 14

What it is you’re going to measure and how often you’re going to take measurements.
E.g. If you are investigating the rate of respiration you could either measure the volume of oxygen used over time or the volume of carbon dioxide produced over time. You could rant measurements at e.g. 30 or 60 second intervals

Question 15

What do you need to choose to use?

Answer 15

The most appropriate appartus, equipment and technique for the experiment

Question 16

Why is it important to choose the right measuring appartus?

Answer 16

It has to be sensitive enough to measure changes you’re looking for . E.g. Measure changes of 1cm3 you need a measuring cylinder that can measure in 1cm3 increments it wouldn’t be any good trying to use into measuring 10cm3 increments it wouldn’t be sensitive enough. If you need to measure a small change in pH a pH meter would be more sensitive than indicator paper

Question 17

What does the equipment and appartus you choose have to be?

Answer 17

Appropriate for the function it needs to perform e.g. If you’re trying to separate photosynthetic ligaments using thin layer chromatography you need to use the right solvent or it won’t separate

Question 18

What does the technique used have to be?

Answer 18

the most appropriate of for your experiment e.g. If you’re growing a culture of microorganisms you need to use aseptic techniques to prevent contamination

Question 19

Describe pipettes

Answer 19

Graduated pipettes have a scale so you can measure specific volumes-make sure you read the meniscus at eye level

Question 20

What is the meniscus?

Answer 20

The curved upper surface of the liquid inside the pipette

Question 21

Water baths describe

Answer 21

Make sure you allow time for water baths to heat up before starting your experiment. Don’t forget that your solution will need time to get to the same temperature as the water before you start the experiment too

Question 22

Data logger

Answer 22

Decide what you are measuring and what type of data logger you will need e.g. Temperature, pH. Connect an external sensor to the data logger if you need to. Decide how often you want the data logger to take readings depending on the length of the process you are measuring

Question 23

What do you need to make sure you’re measuring things using?

Answer 23

Appropriate units e.g. If you’re measuring time, it might be better to use seconds rather than minutes- when you come to processing your results it’ll be easier to work with a result of 73 seconds than a result of 1.217 minutes. Also make sure you record your units properly e.g. If you’re measuring the length of something and accidentally write cm instead if mm any calculations you do will be affected and your conclusion may be wrong

Question 24

What should you make sure you perform?

Answer 24

All techniques carefully that any appartus is set up correctly this will help minimise errors which would affect your results

Question 25

What do you need to carry out when planning an experiment?

Answer 25

A risk experiment

Question 26

What do you need to identify in a risk assessment?

Answer 26

All the dangers in the experiment e.g. Any hazardous chemicals, microorganisms or naked flames
Who is at risk from these dangers
What can be done to reduce the risk wearing goggles or gloves or working in a fume cupboard

Question 27

What else do you need to consider?

Answer 27

Ethical issues in your experiment e.g. For example if you’re using living animals you must treat them with respect. This means handling then carefully and keeping them away from harmful chemicals, extreme heat sources and other things that might cause them physical discomfort

Question 28

How should you display your results?

Answer 28

In a table
Make sure you draw enough rows and columns to record all data you need to. You might also need to include a column for processing your data e.g. Working out an average
Make sure each column has a heading
Units in column heading not in table

Question 29

When you look at all the data in the table what may you notice?

Answer 29

Results that don’t fit with the rest at all anomalous results. You should investigate anomalous results if you can work what happened (you measured badly) you ignore them when processing results. But you can’t just ignore a result if you don’t like it

Question 30

What does calculating percentage change help?

Answer 30

Quantify how much something has changed

Question 31

Percentage change formula

Answer 31

(Final volume- original value)/ original value * 100

Question 32

What does a negative or positive result mean for percentage change?

Answer 32

Positive- means a percentage increase

Negative is a percentage decrease

Question 33

Hoe do calculate the range

Answer 33

Largest value- smallest value

Question 34

Why is standard deviation more useful than the range?

Answer 34

Because it tells you how values are spread about the mean rather than just the total spread of data
A small standard deviation means repeated results are all close to the mean so the results are all similar

Question 35

When van you use the students t-test?

Answer 35

When you have two sets of data that you want to compare
Tests whether there is a significant difference in means of two data sets
Value obtained is compared to critical range which helps you decide how likely that the results or difference in mean were due to chance

Question 36

If the value obtained is greater than the critical region of 5% or less

Answer 36

Then you can be 95% confident that the difference is significant and but due to chance
95% confidence limit which is good enough for biologists

Question 37

If the result is greater than the critical region at a P value of less than 2% or 1%

Answer 37

you can be even more confident that the difference is significant

Question 38

Chi-squared test

Answer 38

Can use chi-squared test when you have categorical (grouped) data and you want to compare whether observed results are statistical different from your expected results. Can compare results to a critical value of its larger the critical value at P=0.05 you can be 95% certain the difference is significant

Question 39

Significant figures

Answer 39

Use most significant figures you typed into calculator to round to

Question 40

If you end up with a very big or a very small number what do you use?

Answer 40

Standard form

Question 41

What graphs and charts?

Answer 41

A great way of presenting data- they can make results much easier to interpret

Question 42

What do you do when you have qualitative data or discrete data?

Answer 42

Use bar charts or pie charts

Question 43

What do you do when you have continuous data?

Answer 43

Use historians or line graphs

Question 44

When can you use a scatter graph?

Answer 44

When you want to plot one variable against the other

Question 45

What should do regardless what type of graph you choose?

Answer 45

Dependent variables on y-axis and independent on X-axis
Label axes using quantity and units and choose sensible scale
Make sure graph covers at least half of the graph paper

Question 46

How do you draw the line of best fit?

Answer 46

Draw line through or as near to as many points as possible ignoring any anomalous results

Question 47

What is rate?

Answer 47

A measure of change over time
Calculating rate can be useful when analysing your data.
Gradient= change in y/ change in X

Question 48

How to find rate of change curve biology style?

Answer 48

By drawing tangent
Position ruler on graph at point where you want to know the rate
Angle the ruler so equal space between ruler and curve on either side of the point.
Draw line along ruler to make tangent
Calculate gradient of tengent to find rate

Question 49

Positive correlation

Answer 49

As one variable increases the other increases

Question 50

Negative correlation?

Answer 50

As one variable increases the other decreases

Question 51

No correlation?

Answer 51

No relationship between variables

Question 52

What does spearman rank correlation coefficient allow you to do?

Answer 52

Work out the degree to which two sets of data are correlated. It is given as a value between 1 and -1. A value of 1 indicates a strong positive correlation. 0 means no correlation and -1 means a strong negative correlation. You can compare your result to a critical value to find out whether or not the correlation is significant.

Question 53

Why do you have to be careful when drawing conclusions?

Answer 53

A correlation between two variables doesn’t always mean that a change in one variable causes a change in the other
Correlation doesn’t equal causation

Question 54

What’s a casual relationship?

Answer 54

Between two variables and a change in one variable does cause change in the other

Question 55

When can it be concluded that a correlation is a casual link?

Answer 55

If every other variable that could possibly affect the result is controlled.

Question 56

Correlations are generally accepted to be causal links when?

Answer 56

Lots of studies have been found the same thing

Scientists have figured out exactly how one factor causes the other

Question 57

What can’t you do when making a conclusion?

Answer 57

A broad generalisation from data you have to be very specific you can only conclude what results show and no more

Question 58

Will your results from an experiment ever be completely perfect?

Answer 58

No there will always be a degree of uncertainty in your measurements due to limits in the sensitivity of the apparatus you’re using
+
- Sign tells you the range in which the true value lies. The range is called the margin for error

Question 59

Percentage error formula?

Answer 59

Uncertainty/ reading *100

Question 60

What’s one clear way to reduce errors in your measurement?

Answer 60

Buy the most sensitive equipment available
In reality there’s not much you can do about this one you’re stuck with whatever your school or college has but there are other ways to lower the uncertainty in experiment
Plan experiment so you weigh a greater amount of something

Question 61

What do you need to assess about your experiment and data?

Answer 61

Repeatability 
Reproducibility
Validity 
Make sure you evaluate your method 
Decide how much confidence you have in your conclusion

Question 62

Repeatability?

Answer 62

Did you take enough repeat reading of the experiment?
Would you do more repeats if you were to do the experiment again?
Do you think you’d get similar results if you did the experiment again?

Question 63

Reproducibility?

Answer 63

Have you compared your results with other people’s results?
Were your results similar?
Could other scientists gain data showing the same relationship that are shown in your data?

Question 64

Validity?

Answer 64

Does your data answer the question you set out to investigate?

Question 65

Make sure you evaluate your method?

Answer 65

Is there anything you could have done to make your results more precise or accurate?
Were there any limitations in your method e.g. Should you have taken measurements more frequently? We’re they any sources of error in your experiment? Could you have used more sensitive apparatus or equipment? Think about how you could refine and improve your experiment if you did it again.

Question 66

If results are repeatable, reproducible and valid and back up your conclusion?

Answer 66

You can have a high degree of confidence in your conclusion