Experimental Design

Question 1

what is the scientific method

Answer 1

• determines what can be studied by science and how it should be studied

Question 2

what are the steps in the scientific method

Answer 2

1. observation = new observations are made and previous data is studied
2. hypothesis = input from various sources is used to formulate a testable statement
3. experiment/observations = the hypothesis is tested by experiment or further observations
4. conclusion = the results are analyzed and the hypothesis is supported or rejected
5. scientific theory = many experiments and observations support a theory

Question 3

what are controlled variables

Answer 3

• ideally, do not change
• common to all treatments

Question 4

independent variable

Answer 4

• what are you altering in the experiment (1 thing changing you control)

Question 5

dependent variable

Answer 5

• what you are observing in the experiment, it should respond to changes in the independent variable

Question 6

what are experimental controls

Answer 6

• results can be internally verified and experimental procedures can be validated using proper controls

Question 7

positive controls

Answer 7

• an experimental treatment which will give the desired result

Question 8

negative controls

Answer 8

• an experimental treatment which will not give the desired result

Question 9

false positive

Answer 9

• type 1 error
• a result seen in the negative control
• detecting something that wasn’t there
• false positive pregnancy test

Question 10

false negative

Answer 10

• type 2 error
• did not detect what it was suppose too
• the positive control didnt work
• negative pregnancy test but still preggo

Question 11

what are other additional concerns

Answer 11

• ruling out experimental or subject biases (blind trials ?)
• has the experimenter taken adequate notes of all materials and methods
• is the experiment reproducible
• is a test qualitative or quantitative
• is a result statistically significant
• can you rule out correlation from causation

Question 12

sensitivity

Answer 12

• minimum amount of X needed to record a positive result ( or give a change on a machine, able to detect smaller changes)

Question 13

specificity

Answer 13

• positive result only comes from a truly positive sample - specific on what you are looking for

Question 14

error: Random Vs systematic

Answer 14

random: new erroe introduced with each measurement (small amount of uncertainty - mistakes that are human or not natural can be good or bad)
systematic : error that is consistently present (constantly present, for every sample, can still counter the error and use the data)

Question 15

accuracy

Answer 15

• how close a single recorded value is to the true value

Question 16

precision

Answer 16

• how reliably you can measure a value (multiple)

Question 17

significant figures

Answer 17

• measurements are limited by precision/accuracy
• when these values are used in a calculation we can not create an answer more precise than the input varibales
• as a rule you should round to the correct number of significant figures only at the end of all calculations

Question 18

basic lab equpiment ; scale

Answer 18

scale must be tared/zeroed with empty container to obtain accurate measurements

Question 19

pipettes

Answer 19

• graduated plastic or glass tubes
• bulbs draw solution in to be measured and dispensed
• volumetric = measure just one volume
• graduated = lines along length determine volume
• serological = calibrated to empty, so need to be emptied when done

Question 20

micropipettes

Answer 20

• p1000 - 100-1000 uL
• p200 20-200 uL
• p20 2-20 uL
• p10 0.5 - 10uL
• adjustable volumes with defined ranged
• disposable tips
• two - step plunger (emptied out final contents with second click)

Question 21

PH and buffers

Answer 21

• pure water dissociates to give 10-7 mol/LH and 10 -7 mol/L OH
  additional acid or base pushes the equilibrium to more H or more OH bu the product of (H) (OH) is always 10-14
• to simplify representing (H) its on a logarithmic scale
  pH= -log(H+)

Question 22

buffers

Answer 22

• mant biological reactions require a defined pH range
• buffered solutions reduce pH fluctuations
• weak acids and bases
• incomplete dissociated gives an equilibruim between acid and conjugate base
• at a specific pH there will be equal amounts of the acid and base in the solution = pKa

Question 23

PH and amino acids

Answer 23

• both the amino and carboxyl ends of an amino acid can act as an acid and base pair
• at a low pH both ends are protonated charge is +1
• at a high pH both ends are deprotonatde and charge is -1
  at a moderate pH the amino end is protonated, the carboyl end is deprotonated and the net charge is neutral

Question 24

storage of solutions

Answer 24

• many chemical solutions have indefinite shelf lives
• some solutions are unstable and need to be made fresh, store aliquotes and prevent exposure to light
• other solutions are food for microorganisms and must be kept steril

Question 25

sterilization for storage of nutrients

Answer 25

- high tempertaures will denature proteins making them non functional - the effectiveness of heat killing is altered by : temperature, time and conductance if any of these are increased, another can be decreased to get the same killing effect

Question 26

steam sterilization

Answer 26

autoclave - boiling point can be inceased by pressure - a higher bioling point gives hotter steam - at 15 PSI steam for boiling water is 121 C

Question 27

filtration of heat labile compounds

Answer 27

- liquids passing through filters which contains holes too small for bacteria to pass - commonly used o.2 uM pore size