2. Variables


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2. Variables

  1. 1. Variables
  2. 2. Q: What is a Variable? A: Anything that can change Examples: use the following headings as a prompt. Environmental/ Physiological Psychological Temperature Time Height Age … Agression Mood Memory Personality Type …
  3. 3. Key Terms Independent Variable (IV): <ul><li>The variable that we manipulate or change </li></ul><ul><li>e.g temperature, noise, organisation of words in a memory test </li></ul><ul><li>The IV can be manipulate naturally </li></ul><ul><li>e.g. gender, age, weather </li></ul><ul><li>An investigation may have more than one IV </li></ul><ul><li>Conditions: </li></ul><ul><li>A condition is a particular manipulation of the IV. </li></ul><ul><li>The IV can have two or more conditions e.g </li></ul><ul><li>Condition 1 : No loud music (control group) </li></ul><ul><li>Condition 2: Loud rock music (experimental group) </li></ul>
  4. 4. Dependent Variable (DV): <ul><li>Is the response that we measure. </li></ul><ul><li>It depends on, or can be affected by the IV. </li></ul><ul><li>e.g the correct number of words remembered. </li></ul><ul><li>or the time taken to do something. </li></ul><ul><li>Note: </li></ul><ul><li>- Sometimes there is no IV and DV as such. </li></ul><ul><li>We do not always deliberately change one to see the effect on another. </li></ul><ul><li>In this case (e.g. observation, correlation, other non-experimental investigations) we only refer to them as variables (variable 1 and variable 2). </li></ul>
  5. 5. Extraneous Variable: <ul><li>Any variable, other than the IV, that may </li></ul><ul><li>affect the DV. </li></ul><ul><li>These can mask the effect of the IV on the DV. </li></ul><ul><li>Researchers should eliminate or minimise their </li></ul><ul><li>influence. </li></ul><ul><li>They can be random factors that affect any </li></ul><ul><li>condition of the IV. </li></ul><ul><li>e.g. There is noise from roadworks </li></ul><ul><li>throughout the memory task </li></ul>
  6. 6. Confounding Variable: <ul><li>Again, a variable other than the IV that affects </li></ul><ul><li>the DV. </li></ul><ul><li>The confounding variable, however, will affect only </li></ul><ul><li>one condition of the IV </li></ul><ul><li>e.g. there is noise from roadworks during only </li></ul><ul><li>one of the conditions. </li></ul>
  7. 7. Activity: For each of the examples below, identify which variable you would manipulate (IV) and which one is measured (DV). <ul><li>Recall is influenced by the amount taken of Drug Z. </li></ul><ul><li>Females conform more than males in bus queues. </li></ul><ul><li>Neutered cats eat more than non- neutered cats. </li></ul><ul><li>Concentration is affected by the time of day. </li></ul><ul><li>Vitamins boost intelligence. </li></ul>
  8. 8. Activity: In pairs complete both the activity boxes on page 197 of Caldwell.
  9. 9. Operational Definitions <ul><li>In Psychology we also have to clearly define the IV and DV in the investigation. </li></ul><ul><li>Operational definitions are detailed practical definitions of the variables which will allow them to be accurately used in a study. </li></ul>e.g In the previous activity we identified the IV and DV for Baddeley (1986). Page 197 Caldwell. IV = acoustic similarity of words, DV = serial memory recall performance.
  10. 10. <ul><li>Operational Definition: </li></ul><ul><li>IV = five short words that sound the same (e.g. man, map, mat, can, cap). </li></ul><ul><li>and five short words that do not sound the same (e.g. pen, day, few, cow, pin). </li></ul><ul><li>DV = The number of correct words recalled. </li></ul>Baddeley (1986) also provides operational definitions to allow them to be accurately used in an investigation.
  11. 11. Task 2: Read carefully the key study on Eye witness testimony by Loftus et al (1978 ) on p. 35 Write the IV and DV for this experiment Write an operational definition for these. Activity: Task 1: For the remaining examples on p. 197 write a suitable operational definition for the IV and DV in the experiments.
  12. 12. Answers: <ul><li>Task 1: </li></ul><ul><li>2) Operational Definition of: </li></ul><ul><li>IV = easy anagram to sort (e.g. doctro) </li></ul><ul><li>more difficult anagram to solve (e.g. cdrtoo) </li></ul><ul><li>DV = Recall of anagrams. </li></ul>
  13. 13. <ul><li>3) Operational Definition of: </li></ul><ul><li>IV = all participants learning words in a distinctive basement room. </li></ul><ul><li> some participants learning words in same distinctive basement room. </li></ul><ul><ul><li> some participants learning words in a fifth floor room with different décor. </li></ul></ul><ul><ul><li> some participants learning words in another room imagining themselves in the basement room </li></ul></ul><ul><li>DV = Memory recall of words learned. </li></ul>
  14. 14. <ul><li>Homework: </li></ul><ul><li>For next Thursday, use the higher text book to make notes on: </li></ul><ul><li>- The meaning of ‘random error’. </li></ul><ul><li>The three main types of extraneous variable (with </li></ul><ul><li>examples) </li></ul>