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Confidence interval (women's heights)

Class Time:


    Student learning outcomes

  • The student will calculate a 90% confidence interval using the given data.
  • The student will determine the relationship between the confidence level and the percentage of constructed intervals that contain the population mean.


Heights of 100 women (in inches)
59.4 71.6 69.3 65.0 62.9 66.5 61.7 55.2
67.5 67.2 63.8 62.9 63.0 63.9 68.7 65.5
61.9 69.6 58.7 63.4 61.8 60.6 69.8 60.0
64.9 66.1 66.8 60.6 65.6 63.8 61.3 59.2
64.1 59.3 64.9 62.4 63.5 60.9 63.3 66.3
61.5 64.3 62.9 60.6 63.8 58.8 64.9 65.7
62.5 70.9 62.9 63.1 62.2 58.7 64.7 66.0
60.5 64.7 65.4 60.2 65.0 64.1 61.1 65.3
64.6 59.2 61.4 62.0 63.5 61.4 65.5 62.3
65.5 64.7 58.8 66.1 64.9 66.9 57.9 69.8
58.5 63.4 69.2 65.9 62.2 60.0 58.1 62.5
62.4 59.1 66.4 61.2 60.4 58.7 66.7 67.5
63.2 56.6 67.7 62.5
  1. [link] lists the heights of 100 women. Use a random number generator to select ten data values randomly.
  2. Calculate the sample mean and the sample standard deviation. Assume that the population standard deviation is known to be 3.3 inches. With these values, construct a 90% confidence interval for your sample of ten values. Write the confidence interval you obtained in the first space of [link] .
  3. Now write your confidence interval on the board. As others in the class write their confidence intervals on the board, copy them into [link] .
    90% confidence intervals
    __________ __________ __________ __________ __________
    __________ __________ __________ __________ __________
    __________ __________ __________ __________ __________
    __________ __________ __________ __________ __________
    __________ __________ __________ __________ __________
    __________ __________ __________ __________ __________
    __________ __________ __________ __________ __________
    __________ __________ __________ __________ __________

    Discussion questions

  1. The actual population mean for the 100 heights given [link] is μ = 63.4. Using the class listing of confidence intervals, count how many of them contain the population mean μ ; i.e., for how many intervals does the value of μ lie between the endpoints of the confidence interval?
  2. Divide this number by the total number of confidence intervals generated by the class to determine the percent of confidence intervals that contains the mean μ . Write this percent here: _____________.
  3. Is the percent of confidence intervals that contain the population mean μ close to 90%?
  4. Suppose we had generated 100 confidence intervals. What do you think would happen to the percent of confidence intervals that contained the population mean?
  5. When we construct a 90% confidence interval, we say that we are 90% confident that the true population mean lies within the confidence interval. Using complete sentences, explain what we mean by this phrase.
  6. Some students think that a 90% confidence interval contains 90% of the data. Use the list of data given (the heights of women) and count how many of the data values lie within the confidence interval that you generated based on that data. How many of the 100 data values lie within your confidence interval? What percent is this? Is this percent close to 90%?
  7. Explain why it does not make sense to count data values that lie in a confidence interval. Think about the random variable that is being used in the problem.
  8. Suppose you obtained the heights of ten women and calculated a confidence interval from this information. Without knowing the population mean μ , would you have any way of knowing for certain if your interval actually contained the value of μ ? Explain.

Questions & Answers

Example of discrete variable
Bada Reply
sales made monthly.
How to answer quantitative data
Alhassan Reply
what's up here ... am new here
sorry question a bit unclear...do you mean how do you analyze quantitative data? If yes, it depends on the specific question(s) you set in the beginning as well as on the data you collected. So the method of data analysis will be dependent on the data collecter and questions asked.
how to solve for degree of freedom
Quantitative data is the data in numeric form. For eg: Income of persons asked is 10,000. This data is quantitative data on the other hand data collected for either make or female is qualitative data.
Degree of freedom is the unconditionality. For example if you have total number of observations n, and you have to calculate variance, obviously you will need mean for that. Here mean is a condition, without which you cannot calculate variance. Therefore degree of freedom for variance will be n-1.
data that is best presented in categories like haircolor, food taste (good, bad, fair, terrible) constitutes qualitative data
vegetation types (grasslands, forests etc) qualitative data
I don't understand how you solved it can you teach me
Caleb Reply
solve what?
What is the end points of a confidence interval called?
lower and upper endpoints
Class members write down the average time (in hours, to the nearest half-hour) they sleep per night.
William Reply
how we make a classes of this(170.3,173.9,171.3,182.3,177.3,178.3,174.175.3)
why is always lower class bundry used
Assume you are in a class where quizzes are 20% of your grade, homework is 20%, exam _1 is 15%,exam _2 is 15%, and the final exam is 20%.Suppose you are in the fifth week and you just found out that you scored a 58/63 on the fist exam. You also know that you received 6/9,8/10,9/9 on the first
Diamatu Reply
quizzes as well as a 9/11,10/10,and 4.5/7 on the first three homework assignment. what is your current grade in the course?
the answer is 2.6
if putting y=3x examine that correlation coefficient between x and y=3x is 1.
Aadrsh Reply
what is permutation
Rodlett Reply
how to construct a histogram
Baalisi Reply
You have to plot the class midpoint and the frequency
ok so you use those two to draw the histogram right.
ok can i be a friend so you can be teaching me small small
how do you calculate cost effectiveness?
Hi everyone, this is a very good statistical group and am glad to be part of it. I'm just not sure how did I end up here cos this discussion just popes on my screen so if I wanna ask something in the future, how will I find you?
To make a histogram, follow these steps: On the vertical axis, place frequencies. Label this axis "Frequency". On the horizontal axis, place the lower value of each interval. ... Draw a bar extending from the lower value of each interval to the lower value of the next interval.
I really appreciate that
umar Reply
I want to test linear regression data such as maintenance fees vs house size. Can I use R square, F test to test the relationship? Is the good condition of R square greater than 0.5
Mok Reply
yes of course must have use f test and also use t test individually multple coefficients
hi frnd I'm akeem by name, I wanna study economics and statistics wat ar d thing I must do to b a great economist
Is R square cannot analysis linear regression of X vs Y relationship?
To be an economist you have to be professional in maths
hi frnds
what is random sampling what is sample error
Nistha Reply
@Nistha Kashyap Random sampling is the selection of random items (or random numbers) from the group. A sample error occurs when the selected samples do not truely represent the whole group. The can happen when most or all of the selected samples are taken from only one section of the group;
Thus the sample is not truely random.
What is zero sum game?
Hassan Reply
A game in which there is no profit & no loss to any of the both player.
Differences between sample mean & population mean
mohammed Reply
Not difference in the formula except the notation, sample mean is denoted by x bar and population mean is denoted by mu symbol. There is formula as well as notation between difference variance and standard deviations
Likely the difference would be in the result, unless the sample is an exact representation of the population (which is unlikely.)
what is data
Nii Avin - Data is just a simple way to refer to the numbers in the population, or in the sample used in your calculations.
what are the types of data
Data is the very pale android from the Star Trek Enterprise
Am Emmanuel from Nigeria
Am Qudus from Nigeria
am Handson from Cameroon
what is a mode?
Nii - data is whatever you are sampling. Such as the number of students in each classroom.
Handson Ndintek - the mode is the number appearing most frequently. Example: 7 9 11 7 4 6 3 7 2. 7 is the mode. In a group such as 7 9 1 4 6 3, there is no mode because no number appears more often than any other.
hi I want to know how to find class boundary
give me the two types of data
Neddy Reply
qualitative and quantitative
primary and secondary data
qualitative and quantitative

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