"Shark attacks are most likely to occur on Sunday, in less than 6 feet of water, during a new moon and involve surfers wearing black and white bathing suits, a first of its kind study from the University of Florida suggests." is the leading sentence of a May 2010 dated article in the University of Florida News. Researchers investigated all shark attacks in the area between Daytona Beach and New Smyrna Beach, the coastline infamous for its number of shark attacks, over a period of more than 50 years. But it is not only Florida that has a keen interest to discover the 'why, where and when' of shark attacks. In this case study, we will look at shark attacks from another data collection: www.sharkattackfile. net. It records data on all shark attacks in recorded history, going back to before 1800. Included is all known information on the shark attack such as the date, location, information on the individual who was attacked, details on the injuries sustained by the victim, and the species of the shark. The data file is large: it contains 5937 different attacks. Since we are primarily interested in the recent past, let us select those cases that happened in the 2000's. StatCrunch can help us with this selection. A last preparation of the data set refers to distinguishing between Florida and non-Florida attacks: we are interested to see whether attacks in Florida are similar or different than attacks outside Florida. We do so by creating a new variable, an indicator or dummy variable, signaling if the attach took place in Florida or not. StatCrunch Data Set Find the descriptive statistics of the age of people attacked by sharks after 1999, both for fatal and non-fatal attacks. Find the mean ages of people involved in non-fatal and fatal shark attacks. The mean age of people involved in non-fatal attacks is 29.49 (Round to two decimal places as needed.) The mean age of people involved in fatal attacks is 33.03 (Round to two decimal places as needed)
Solution
Step 1 ：First, we need to filter the data to include only those cases that happened after 1999. This can be done using the 'year' column in the data set.
Step 2 ：Next, we separate the data into two groups: fatal attacks and non-fatal attacks. This can be done using the 'fatal' column in the data set.
Step 3 ：For each group, we calculate the mean age of the victims. This can be done using the 'age' column in the data set.
Step 4 ：The mean age of people involved in non-fatal attacks is calculated as follows: \[ \frac{\sum_{i=1}^{n} age_{i}}{n} = 29.49 \] where \(age_{i}\) is the age of the victim in the i-th non-fatal attack and n is the total number of non-fatal attacks.
Step 5 ：The mean age of people involved in fatal attacks is calculated as follows: \[ \frac{\sum_{i=1}^{m} age_{i}}{m} = 33.03 \] where \(age_{i}\) is the age of the victim in the i-th fatal attack and m is the total number of fatal attacks.
Step 6 ：Therefore, the mean age of people involved in non-fatal shark attacks is \(\boxed{29.49}\) and the mean age of people involved in fatal shark attacks is \(\boxed{33.03}\).
