STATS Lec 8- Independent and dependent variables

Question 1

Independent vs Dependent variables

Answer 1

• Independent IV:
  
  • The variable that is manipulated or in some other way is hypothesised to bring out the change in the dependent variable
  • Sometimes called CONDITION.. See later
• Dependent DV:
  
  • The variable upon which is study depends. Usually, the variable that is measured (the outcome variable)

Question 2

An experiment

Answer 2

• Does the number of colonies grown depends on the type of agar used
• IV: type of agar
• DV: number of colonies

Question 3

Another experiment

Answer 3

• Does chocolate intake vary with age
• The IV is AGE
• The DV is chocolate consumption

Question 4

Independent variables: levels

Answer 4

• Independent variables each have at least 2 levels that are typically compared with one another in a given study
• E.g. if the IV is age
  
  • 2 levels: young (<50) old (>50)
  • 6 levels: 0-15, 15-30, 30-45, 45-60, 60-75, 75-100 years of age

Question 5

Independent vs dependent variables

Answer 5

• H: students who attend lectures regularly will get higher marks
• IV: number of lectures attended in the course (high lecutre attendees/low lecture attendees)
• DV: Final mark in the course
• How many levels IV

Question 6

Independent vs dependent variables

Answer 6

• H: adding fetal calf serum to growing medium will increase the number of cells in a culture
• IV: with FCS/Without FCS
• DV: number of cells in each flask
• How many levels IV

Question 7

Identify the IV and DV

Answer 7

• A researcher is intrested in the effect of sleep deprivation on reaction time
• She assigned each of 60 psychology students to one of four conditions for which the students were deprived of sleep for: 0 days, 1 days, 2 days, 3 days
• She then measured the average reaction time of students in each conditions
  *

Question 8

IV levels DV

Answer 8

• A scientist wanted to see how temperature affected the rate of reaction between 2 colourless liquids that combined to form a coloured salt
• He ran the experiment 5 times at 5 different temperatures 0, 10, 20, 40 and 80’C
• He measured the time to colour change
• A lab technician investigated the effect of a novel supplement on the development of cell biomass
• She compared the biomass grown in fermentation vessels without and with the supplement
• The technician repeat the last experiement but this time tried 3 different concentrations of growth supplement, 0.1%, 0.5% and 1%
• How many levels of IV?