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Edexcel AS Biology Unit 3 9th May 2016 Official Thread

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Why is it then that when questions in the papers come on commenting on the reliability of a set of data, in the ms overlapping standard deviations are discussed?

When there is overlapping it also decreases the reliability of the experiment. What exactly does the mark scheme say about overlaps?

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Reply 41

Neurology

Original post by Saima Hasnain

When there is overlapping it also decreases the reliability of the experiment. What exactly does the mark scheme say about overlaps?

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i think you made a mistake here. when s.d. overlaps for two sets for data, we say that the overlapping range for that data is not significant.

Reply 42

Mariam_

guyys does anyone have extra notes on Vitamin C experiment
most people say that its most likely to come I really hope so

Reply 43

Neurology

Original post by bdoon esm

When to draw a bar chart and when to draw a scatter graph and a straight line graph?

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bar chart - the independent variable is a qualitative value rather than a quantitative. thereby, your x axis would not have any numbers involved.

scatter/straight line - in bio, we have to connect the points, unless they have specifically asked to draw a straight line

Reply 44

Hiyoriiki

Original post by Saima Hasnain

When there is overlapping it also decreases the reliability of the experiment. What exactly does the mark scheme say about overlaps?

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Its usually in the comment on reliability qs so in the ms it says that we just state if and where is the overlap

Reply 45

Saima Hasnain

Original post by Neurology

i think you made a mistake here. when s.d. overlaps for two sets for data, we say that the overlapping range for that data is not significant.

Oh, what do you mean by not significant?

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Reply 46

Neurology

Original post by Saima Hasnain

Oh, what do you mean by not significant?

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we dont consider it when making conclusions

Reply 47

Saima Hasnain

Original post by Hiyoriiki

Its usually in the comment on reliability qs so in the ms it says that we just state if and where is the overlap

Oh okay, thanks 😊

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Reply 48

Saima Hasnain

Original post by Neurology

we dont consider it when making conclusions

Oh okay, thanks alot ☺️

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Reply 49

Neurology

Original post by Saima Hasnain

Oh okay, thanks alot ☺️

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glad to help :biggrin:

Reply 50

Hiyoriiki

Did anyone understand jan 12 (c)(i)? (Q1)

(edited 7 years ago)

Reply 51

Nethmioysters

Original post by Neurology

we dont consider it when making conclusions

so if the SDs overlap and they ask us to comment on the reliability, should we say its not reliable ?

Reply 52

charlesdarwin

what about the totipotency experiment?

Reply 53

Ali Bizri

Original post by Willandy123

How do you know vitamin C is gonna come tomorrow?

There's a pattern in the exams,

jun 09: membrane
jan 10:garlic
jun 10:enzymes
jan 11:minerals
jun 11;fibres
jan 12:vitamin
jun 12:caffeine
jan 13:toti
jun 13:mitosis
--------
jan 14:membrane
jun14:garlic
jan 15:enzymes
june 2015 --> mineral
jan 16: Fibres
June 16:Vitamin??

So basically, it's really likely to actually be Vitamin C

Reply 54

Nethmioysters

Do we need to memorise the whole experiment or should we just learn about the independant, dependant and controlled vairables and also the reagents used?

Reply 55

charlesdarwin

Original post by Nethmioysters

so if the SDs overlap and they ask us to comment on the reliability, should we say its not reliable ?

if they overlap, it is NOT reliable, coclutions should not be made

Reply 56

Nethmioysters

Original post by charlesdarwin

if they overlap, it is NOT reliable, coclutions should not be made

oh ok thanks!!!!

Reply 57

Nethmioysters

Original post by Willandy123

To increase validity:
1) Compare experimental results with other similar experiments
2) Use of control in experiment.
3) Check bias of sponsors.
4) No overlapping of standard deviation.
5) Large sample.
6) Peer review.
7) Methodology to which the data is obtained.

Keeping all other factors constant increases reliability because we would without doubt know that all changes within an experiment is due to the specific factor. For example: Mineral deficiency, we need to find out the effect of mineral deficiency in plants so variables to keep constant are light intensity and temperature. Now, we want to make sure that all changes in growth of plants is due to mineral deficiency but not light intensity and temperature, therefore makes the results more reliable.

Hopefully this helps as I am also going to take the exam.

This is great! thanks!

Reply 58

charlesdarwin

dependent and independent variables in vit c experiment?

Reply 59

Ali Bizri

Original post by Hiyoriiki

Didn't overlapping standard deviations decrease validity?

Oh yes, overlapping standard deviations DO make the data unreliable, what i meant was that in general, If a table shows high SD then the data is unreliable.