A tea company sells boxes of tea bags with a stated weight of 125 g. A consumer watchdog suspects that the mean weight of these boxes is less than the stated weight. They weigh a random sample of 80 boxes and find the weights have a mean of 123.5 g and a standard deviation of 4.2 g.
Using a 1% level of significance, test whether or not the watchdog's suspicion is justified. State your hypotheses clearly.
Find the 95% confidence interval for the mean weight of a tea box from this production line.
Based on your findings, state the advice that should be given to the tea company regarding the weight of their boxes.
The tea company upgrades their machinery, resulting in a new mean weight μ\muμ and a reduced standard deviation of 2.5 g. A researcher takes a sample of size nnn and uses the sample mean Xˉ\bar{X}Xˉ as an estimator of μ\muμ.
Find the minimum value of nnn such that P(∣Xˉ−μ∣<0.5)≥0.99P(|\bar{X} - \mu| < 0.5) \ge 0.99P(∣Xˉ−μ∣<0.5)≥0.99.
Practise Edexcel A Level Maths The Normal Distribution with exam-style questions for A Level Maths. 439 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
