If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: Statistics and probability>Unit 6

Lesson 3: Sampling methods

# Samples and surveys

When we collect data it's important to know what type of data we're collecting and how to collect it properly.

## Problem 1: Qualitative and quantitative data

A survey was given that included data on each student's field of interest, age in years, number of languages spoken, and handedness.
DavidBeccaPaige...
Field of interestcomputer sciencejournalismchemistry...
Age (years)$13$$15$$14$...
Languages spoken$2$$1$$1$...
Handedrightleftright...
question a
Is "field of interest" qualitative or quantitative?

Question b
Is "age (years)" qualitative or quantitative?

Question C
Is "languages spoken" qualitative or quantitative?

Question D
Is "handed" qualitative or quantitative?

## Problem 2: Representative samples

question a
Jillian wants to know what percent of students at her school watch sports on TV. Which strategy for sampling will be more likely to produce a representative sample?

question b
Theo wants to know what percent of students at his school have a computer. Which strategy for sampling will be more likely to produce a representative sample?

## Problem 3: Sampling methods

Willy wants to find what percent of students at his school drink the milk after they finish their cereal. He is considering the following sampling methods:
question a
He selects every tenth person who enters the school. What type of sampling is this?

question b
He randomly selects $10$ students from each grade level (freshman, sophomore, junior, senior). What type of sampling is this?

question c
He randomly selects $50$ student names from a hat. What type of sampling is this?

question d
He randomly selects $3$ classrooms and surveys every student in those classrooms. What type of sampling is this?

## Problem 4: Biased wording in survey questions

Willy wants to find what percent of students drink the milk after they finish their cereal. Which survey question below is the most unbiased?

## Want to join the conversation?

• what does this have to do with math?
• Math include statistics, which is counting and making data.
• why wouldn't it be random if he pick every tenth student he didn't know the tenth student every time. My teacher explained this to me. I think there should have been to answer choices
(1 vote)
• "every 10th" makes it a systematic approach. the student chosen will still be random, but the way he chooses the student is not random

In Problem 1, we suddenly had to decide whether or not data was "qualitative". During the lessons and previous quizes, this was called "categorical".

In Problem 3, we suddenly had to decide whether or not as sample was "Randow" - During the lessons and the previous quizes this was called "Simple Random" ...
• This is very frustrating. I have watched all KA videos in order up to HS Stats that this "lesson" is in and there are several questions about topics that were never even touched on. KA, please fix this.

Though I did get a laugh out of the last question ""Do you drink the disgusting leftover milk after you finish your cereal?""
• what is the most effective type of sampling ? and is there way to know that the sampling type i select is good representative of the population ??
thanks
• The lesson confuses "nature of study" with "data types." Data is neither qualitative nor quantitative. The questions that ask this are misleading. Data have types. Name/favorite food... nominal; Age... ordinal; Handedness/Gender... categorical; Height... continuous; etc.
Qualitative and quantitative refer to how you use the data. Even with purely nominal data, quantitative studies can be performed.

Also, the lessons and quizzes create confusion with respect to the handling of sample data (i.e., experiment vs. observation). In the unit test, there are several multiple choice answers that list (a) sampling, (b) experiment, (c) observation, when these are not treated equally in the lessons. In the lessons, "experiment" and "observation" are treated as subordinate to samples, at least at the early location.
(1 vote)
• There are some questions i did not under stand like the Random,Systematic,Stratified,and cluster questions
(1 vote)
• Disgusting left overs?😭🤣
(1 vote)
• fr
😭
(1 vote)
• This survey was super easy