According to a 2019 study by RescueTime, people spend an average of 1.25 minutes on their smartphone each time they pick it up. If Noelle's distribution of smartphone use is approximately normal with a mean of 1.25 minutes and a 97th percentile of 2 g minutes, calculate its standard deviation

Does the age of the Covid-19 infections follow a normal distribution? Why or why not?

The lifetime of a particular component is normally distributed with a mean of 1000 hours and a standard deviation of 100 hours. What is the 80th percentile of component lifetimes?

Bone mineral density (BMD) is a measure of bone strength. Studies show that BMD declines after age 45. The impact of exercise may increase BMD. A random sample of 59 women between the ages of 41 and 45 with no major health problems were studied. The women were classified into one of two groups based upon their level of exercise activity: walking women and sedentary women. The 39 women who walked regularly had a mean BMD of 5.96 with a standard deviation of 1.22. The 20 women who are sedentary had a mean BMD of 4.41 with a standard deviation of 1.02. Which of the following inference procedures could be used to estimate the difference in the mean BMD for these two types of women