Codebusters Test Data-Driven Instruction 5

Question 1

A Codebusters instructor uses assessment data to teach students about letter contact frequency. Which letter in English has the highest frequency of appearing adjacent to the letter E?

Accepted Answer

R

Answer

Q

Answer

Z

Answer

X

Question 2

A team reviews competition data and finds poor performance on cipher type identification. Which statistical property most reliably distinguishes a Caesar cipher from a Vigenère cipher?

Accepted Answer

Index of Coincidence—Caesar scores ~0.065 while Vigenère scores closer to 0.038–0.050

Answer

Total number of unique symbols used

Answer

The presence or absence of numbers in the ciphertext

Answer

Whether the ciphertext length is odd or even

Question 3

A student applies data-driven instruction and builds a contact table. What is a 'contact table' used for in cryptanalysis?

Accepted Answer

Recording which letters appear before and after each ciphertext letter to identify common plaintext patterns

Answer

Tracking how many times each letter was guessed correctly

Answer

Listing all possible keyword lengths for a Vigenère cipher

Answer

Counting the total occurrences of each number in a numeric cipher

Question 4

After reviewing error logs, a Codebusters coach notes students struggle with xenocrypt ciphers. What makes a xenocrypt different from a standard aristocrat?

Accepted Answer

Xenocrypts are monoalphabetic substitution ciphers of text written in a foreign language

Answer

Xenocrypts use numbers instead of letters

Answer

Xenocrypts scramble word order rather than substituting letters

Answer

Xenocrypts always use the Vigenère method

Question 5

A coach tracks data showing students fail to apply columnar transposition analysis correctly. In a simple columnar transposition cipher, what determines the column order during decryption?

Accepted Answer

The alphabetical order of the letters in the keyword

Answer

The frequency of the most common letter in the ciphertext

Answer

The number of letters in the plaintext message

Answer

The Index of Coincidence value

Question 6

Using item analysis data, a teacher finds students rarely check for the word pattern 'X__' (three-letter word, first and last letter same). What common English word fits this pattern?

Accepted Answer

DID

Answer

THE

Answer

AND

Answer

FOR

Question 7

A student applies data analysis to a ciphertext and identifies that 30% of all symbols are a single character. What does this high single-character dominance most likely suggest about the cipher?

Accepted Answer

The cipher is likely a simple Caesar or ROT-based shift where one common letter like E is mapped to a single symbol

Answer

The cipher uses a very long Vigenère key

Answer

The cipher uses base-64 encoding

Answer

The message contains mostly numbers