Everything Maths Grade 11

CHAPTER 18. STATISTICS 18.5

Extension: Ohm’s Law

Ohm’s Law describes the relationship between current and voltage in a conductor. The gradi-

ent of the graph of voltage vs. current is knownas the resistance of the conductor.

Activity: Scatter Plot

The function that best describes a set of data can take any form. We will restrict ourselves

to the forms already studied, that is, linear, quadratic or exponential. Plotthe following sets of

data as scatter plots anddeduce the type of function that best describesthe data. The type of

function can either be quadratic or exponential.

1.

x y x y x y x y

− 5 9. 8 0 14. 2 − 2. 5 11. 9 2. 5 49. 3

− 4. 5 4. 4 0. 5 22. 5 − 2 6. 9 3 68. 9

− 4 7. 6 1 21. 5 − 1. 5 8. 2 3. 5 88. 4

− 3. 5 7. 9 1. 5 27. 5 − 1 7. 8 4 117. 2

− 3 7. 5 2 41. 9 − 0. 5 14. 4 4. 5 151. 4

2.

x y x y x y x y

− 5 75 0 5 − 2. 5 27. 5 2. 5 7. 5

− 4. 5 63. 5 0. 5 3. 5 − 2 21 3 11

− 4 53 1 3 − 1. 5 15. 5 3. 5 15. 5

− 3. 5 43. 5 1. 5 3. 5 − 1 11 4 21

− 3 35 2 5 − 0. 5 7. 5 4. 5 27. 5

3.

Height (cm) 147 150 152 155 157 160 163 165

168 170 173 175 178 180 183

Weight (kg) 52 53 54 56 57 59 60 61

63 64 66 68 70 72 74

DEFINITION: outlier

A point on a scatter plot which is widely separated from the other points or a result

differing greatly from others in the same sample is called an outlier.

See video: VMgao at http://www.everythingmaths.co.za

Exercise 18 - 5

1. A class’s results for atest were recorded alongwith the amount of timespent studying for it. The
   results are given below.