equations 😟 Flashcards
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What is m1 x v1 = m2 x v2
(Finding v1 usually)
Concentration of orig sol. x vol of orig sol.
=
Conc by end (TOTAL) x vol by end (TOTAL)
10 represents m1 (unless otherwise)
The (eg. 5ml) solution is v2
Final conc is on table
How do we use a calibration curve
- Make different known sugar concentrations
- Use colorimeter to measure absorbance/transmission
Of each conc and plot cal curve on graph - Find conc of sample from calibration curve
How to find uncertainties
Amount of uncertainty is
+/- half the smallest division on the scale measuring with
Eg. Smallest division is 5ml
+/- 2.5 ml
80ml +/- 2.5
…
With 2 or more uncertainties
1. Find all uncertainties
2. Add measured volumes
3. Add to get combined uncertainty
4. Combine answers from last 2 steps to get the total volume and uncertainty
NEEDED SAME UNITS
How to work out percentage error
(Uncertainty/ measured value) x100
How to describe using a calibration curve to find unknowns
- make different known sugar concentrations
- use colorimeter to measure absorbance of each conc
- plot calibration curve on graph
- find conc of sample from using curve
Mitotic index
( Cells in mitosis / total cell no. ) x 100
= percentage of cells undergoing mitosis
Why do we use percentages
Allows comparisons between different starting values
What to put for evaluating questions (studies)
+ tends to be data fitting pattern (quote)
- no control
- untruthful/subjective response
- some data not fitting pattern(quote)
- done in animals not humans
- small sample is unrepresentative
- one group (eg. Male)
- correlation not causation
What are statistical tests for and what are null hypotheses
Tell us whether patterns in data are due to chance or real differences
No statistical difference = due to chance (accept)
Eg. Will be no statistically significant difference/correlation
Between both variables
Critical value and P value - what is it
It’s an estimate of probability that result occurred
By statistical accident
If p value is large, unlikely statistical significance (by chance)
If p value is small, likely statistical significance (not chance)
p value = 0.05 (means less than 5% chance that it’s due to chance)
,.
To work out if less than 5% chance it’s due to chance
The CRITICAL VALUE has to be greater/equal to TEST STATISTIC (given)
To be a statistically significant difference/correlation (reject)
The CRITICAL VALUE has to be lower that TEST STATISTIC
to be by chance (accept)
What’s the degrees of freedom
Along y axis of table.
It’s the number in sample (in chi square, category number) MINUS 1
The x axis is the p value (0.05)
Find what they make when they meet = critical value
Different types of stats tests
• T test
Finding if there’s a difference between means of two data sets
Two sets of data measure same thing (DV)
But are two conditions
—> distribution graph
• chi squared
Finding if there’s a difference between expected and observed data
Measure same things (DV) . Data’s from different conditions
—> bar chart
•spearman’s rank
Finding if correlationbetween two variables
Which are completely different (diff units)
Two sets of data measuring different things (see if correlation)
—> scatter graph
What are logarithmic scales
Hard to plot large values on a graph, where data is so spread out
—> log scales go up in order of magnitude, so each mark on scale 10x bigger than last
- eg pH
- bacteria growth
- richter scale
How to do..
Using log then typing in value
Tells you how many times 10 has been multiplied by itself to get the value
Shift then log and then typing value
Tells the opposite (the original value from log)
What are uncertainties
Uncertainty is +/- half the smallest division on a scale
You’re measuring with
Balance eg goes up in 10g so uncertainty is +/-5g
—> ie margin of error is 5g each side (10g)
