lab 3 - the chi square test & critical calculations & pipetting

chi-square test

statistical test used to determine how well the observed phenotypic ratios match the expected phenotypic ratios given the hypothesized pattern of inheritance

If the results indicate that the difference between the observed data & the expected data could be due to chance

the hypothesized pattern of inheritance is supported

If the test indicates that the difference between expected & observed data is not likely to be due to chance, the difference is significant

the hypothesized pattern of inheritance is rejected

null hypothesis

The difference found between observed distribution & expected distribution is not significant

any difference is due to random chance

calculated χ2 ≤ critical χ2

“fail to reject” the null hypothesis

no significant difference

alternative hypothesis

difference found between observed distribution & expected distribution is significant (in a specific direction/amount)

Difference is not due to chance alone

critical χ2 ≤ calculated χ2

we reject the null hypothesis

there is a significant difference

Degrees of Freedom

Degrees of Freedom = # Phenotypes – 1

P-Value

You are allowing for 5% error in accepting a hypothesis that should really be rejected.

95% Confidence in “failing to reject”

Critical Value (X² _P-Value)

Obtained at intersection of p-value & Degrees of Freedom.

The limitation at which we reject the null hypothesis

dimensional analysis

a method of converting between units

a form of proportional reasoning where a given measurement can be multiplied by a known proportion or ratio to give a result having a different unit or dimension

order of magnitude

the relative size of a number

Often used in comparison between 2 numbers

Refers to the power of 10 that can be factored out of a number

significant figures

digits in a number that contain meaningful information about the value, but not the order of magnitude

mole (mol.)

Name for 6.022 x 1023 particles of something

1 mole = 6.022 x 10²³ molecules

molar (M)

adjective which describes the concentration of a solution in moles per liter (mole/L)

molarity

the moles of solute per liter of solvent

The molarity of a solution is the number of moles per liter (mol/L) in that solution

C₁V₁=C₂V₂

C1= Concentration of stock solution

V1= Volume of stock solution

C2= Concentration of final solution

V2= Volume of final solution + volume of solvent

serial dilution

executed by conducting a SERIES of simple dilutions which amplifies the dilution factor quickly; it usually begins with a very small initial quantity of material

aliquot

a measured sub-volume of the original sample

Aliquot = Final Volume / Dilution Factor

dilutant

material with which the sample is diluted (i.e., Solvent, diluent)

Dilutant = Final Volume – Aliquot

dilution factor

is the total number of unit volumes in which your material will be dissolved Dilution Factor = Final Concentration/Initial Concentration = Final Volume/Aliquot

precision

measure of how closely the data agree with each other or how close they cluster together

accuracy

how close the measurements, or their mean, are to the actual (true) value

pipetmen

tools for accurately dispensing fluids

accurately measuring & dispensing these small volumes are essential to performing many scientific experimental procedures

reading the volume