Lesson 4 Inference and box plots
Focus • Inferring back to the population • Box plots
PROBLEM • Do boys at Karekare College tend to have longer popliteal lengths than girls at Karekare college?
DATA • Sample of 30ish boys and 30ish girls from Karakare College
ANALYSIS • I notice… • Write three I notice statements about this graph…
ANALYSIS • I notice… (describe what is happening in your samples) • I wonder… (inferential statement about what might be happening back in your population)
Box plot reminder MEDIAN – halfway through ordered data • Mark the middle of all the values… • How do we find this? • Odd/even sample sizes? • What is the name of this STATISTIC?
QUARTILES–quarter of the way through ordered data Box plot reminder • Mark the middle of the bottom half and the middle of the top half… • How do we find this? • Median included or not? • What is the name of these STATISTICS?
Box plot reminder • Join these three values up with a box • The middle value is a line through the box • Extend a line from the box to the smallest and largest values • Congratulations – you’ve made a box plot!
Box plot reminder • Box plots split the data up into quarters • We often refer to the middle 50% which is the box part.