Grade 10 – Introduction to Correlational Studies



Part I) Introduction to Correlational Studies and Variables

An experiment is an activity in which one or more independent ('cause') variables are forced to change. For example, to test the effect of different types of soils on bean plant growth, we could conduct an experiment by using several types of soils (independent [‘cause’] variable) and measure how high the bean plant grows (dependent ['result'] variable).

Instead, we could find some bean plants in nature, measure their heights and examine the type of soil in each case. We can then see if there is a relationship between plant height and type of soil. This type of inquiry would be a study, not an experiment. The independent ('cause') variable is allowed to change naturally. It also would be a correlational study, because we would be comparing (correlating) how changes in one variable (e.g., types of soil) may affect changes in another variable (e.g., plant height).

Correlational studies are useful when it’s not ethical to measure the changes in the result variable resulting from certain cause variables. With types of soil and bean plant growth it would be better to conduct an experiment anyways. However, if we wanted to study the relationship between smoking and people who develop lung cancer, then we would conduct a study. It’s not right (ethical) to force one group of people smoke and see if they develop lung cancer.

1) Using the following table, match each cause variable with its result variable. More than one possible answer can exist.

|Cause Variables (Independent) |Result Variables (Dependent) |

|vegetarianism |teenagers’ hearing |

|rock music |teenagers’ learning |

|exercise |plant height |

|hormones |growth of bacteria |

|drugs |aggressive behaviour |

|T.V. watching |physical fitness |

|temperature |muscle strength |

2) How would you conduct the following investigations? Would you perform an experiment or conduct a study? Identify independent and dependent variables in each case (IV/DV). Also, think about what you would have to control!

a) The effect of cigarette smoking on the amount of coughing

|Study |Experiment |I.V: |D.V: |

b) Solubility of salt at various temperatures

|Study |Experiment |I.V: |D.V: |

c) Amount of time spent in front of the computer and quality of sleep

|Study |Experiment |I.V: |D.V: |

d) The effect of pH on corrosion of metal

|Study |Experiment |I.V: |D.V: |

e) Time you spend playing video games and your grades in school

|Study |Experiment |I.V: |D.V: |

Part II) Getting ready to perform a study – Practice collecting data in class and determining the correlation between two variables

Question 1: Is there a correlation between reaction time and gender?

Question 2: Is there a correlation between reaction time and your chosen variable?

Data Collection Table:

|Student Name |Gender |Reaction Time |_____________ |

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Analysis:

1) Develop a bar graph to show the average reaction times by females and males. State if there is any correlation between gender and reaction time in our class.

2) Develop a scatter plot of reaction time (Y-axis) and _________ (X-axis). Determine if there is a correlation between ______________ and reaction time for the students in our class.

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