Noemi Saenz
Week 6 Lab
Suppose we use the branded toothpaste of popular company. Company claims that the average weight
of the packaged toothpaste is 150 gram. For finding the confidence interval for the population average
weight of the packaged toothpastes, we need to collect the data for weights for toothpastes. For this
purpose, we will collect 10 to 15 non-used and new toothpastes of same company. We will use the same
product of 150 gram. Then we will collect weights of collected toothpastes. We will try to use random
sampling for selection of toothpastes if possible. After collecting the weights, we will find out sample
standard deviation S, sample mean Xbar, sample size n, degrees of freedom, etc. We will consider 95%
confidence interval for the population average weight of the branded toothpaste. We will use following
formula for calculation of confidence interval:
Confidence interval = Xbar -/+ t*S/sqrt(n)
Where, t is the critical value which is finding out by using t-table or excel.
Using above formula, we will find out the lower limit and upper limit for the confidence interval. For the
next use, if the average weight of the sample of toothpastes is not lies within upper and lower
confidence limits, then we will reject the hypothesis that the weight of the toothpaste is 150 gram.
In the same manner we will find out confidence intervals for other products. Also, we will find out
confidence intervals for standard deviations, proportions, etc.