6.15 MALICIOUS ATTACKS ON A CRYPTOCURRENCY NETWORK. Refer to the Computers & Security (January 2020) study of a software system developed for cryptocurrency, Exercise 2.25 (p. 59). Recall that the researchers developed a detector of malicious attacks on data traveling through the network. A key detection variable was the size (number of bytes) of a traveling data packet. The researchers discovered that when not under attack (i.e., in a normal state), the true mean size of data packets traveling through the network is 337 bytes. To estimate the mean size of data packets that are under a malicious attack, the researchers sampled 130 data packets in the attack state. The sizes of these 130 packets are saved in the ATTACK file(where State="Attack").

a. Refer to the histogram of the 130 data packet sizes shown in Exercise 2.25. Will the non-normal shape of this histogram prevent you from assuming that the sampling distribution of x is approximately normal? Why or why not?

b. Use statistical software to obtain a 95% confidence interval for the true mean size of the data packets in the attack state. Give a practical interpretation of the result.

c. One theory is that when under a malicious attack, the mean size of the data packets will be less than when in a normal state, i.e., less than 337 bytes. Is there evidence to support this theory? Explain.