6.1.3 Homework Answers

[Libby Cowen]

Howare learners answering questions? In edX Insights, graded contentsubmissions show you the responses that learners submit for graded problems,and help you evaluate what they find difficult. To illustrate, this sectionpresents the Analytics in Action section first.

For problem types that provide both the question and a set of possible answers(checkboxes, dropdown, and multiple choice), submission data helps you assesshow difficult it is for learners to identify and submit the correct answer.The submissions chart provides a visual contrast of the number of learnerswho select incorrect answers with the number who answer correctly.

For open-ended problem types that provide only the question (numerical, text,and math expression input), submission data can help you identify similarresponses. In the Submission Counts report, you have access to every answersubmitted by a learner. The chart, however, presents only the 12 mostfrequently submitted responses. Your initial investigation into how learnersanswer a question can begin with this set of 12.

Before the release date of each section, you encourage your beta testers toanswer every question and to submit both correct and incorrect answers.You then use edX Insights to review the answers that your testers submit foreach problem. You verify that each problem is set up as you intend, andcorrect any oversights before learners can encounter them.

In this way, you can use edX Insights to validate the grading configuration,and to proofread the display names, accessible labels, and text that you haveprovided for the graded assignment types, assignments, problems, questions,and answers.

In another example, you use edX Insights to check the answers that your betatesters submitted for one of the questions in a quiz. You notice that the chartfor this question does not have a title. For this problem component, youneglected to identify the question with an accessible label.

After you select Performance and Graded Content, edX Insights displaysthe assignment types that make up the grading configuration of the course. Youuse the drop-down Select Assignment Type menu or click an item in thegrading configuration to select the assignment type to investigate.

The Assignment Submissions report on this page provides the number of problemsin each assignment. The report also includes the correct and incorrectsubmissions received. These values are averaged by the number of problems ineach assignment.

After you select an assignment, edX Insights displays a stacked bar chart thatsummarizes learner performance on each problem in that assignment. In thisexample from the edX Demo course, the selected homework assignment includesjust one problem.

If the problem that you select includes more than one part (or question), thefirst part appears. To select a different part, you use the Submissions forPart number drop-down. In the Demo course example, the selected homeworkproblem has three parts.

After you select a problem or problem part, edX Insights displays submissiondata in a bar chart and a report that you can view or download. Descriptionsof the chart and report follow. For detailed information about thecomputations, see Computation Reference.

Problems that use the Randomization setting in Studio result inmany possible submission variants, both correct and incorrect. As a result,edX Insights does not attempt to present a chart of the responses submittedfor these problems. You can download the Submissions Counts report toanalyze the answers that are of interest.

The bars on this chart represent the number of enrolled learners who submitteda particular answer to a question in a problem component. The x-axis includesthe most frequently submitted answers, up to a maximum of 12. Due to spacelimitations, the answer text that is used to label the x-axis might betruncated. Moving your cursor over each bar shows a longer version of theanswer.

To review the problem component in the LMS as a learner sees it, select ViewLive and then at the top of the page use the View this course as optionto select Learner. The LMS displays the page that contains this problem inLearner View. For more information, see View Your Live Course.

A report with a row for each problem-answer combination submitted by yourlearners is available for review or download. The report columns show eachsubmitted answer, identify the correct answer or answers, and provide thenumber of learners who submitted that answer.

The report includes one row for each problem-answer combination submitted by alearner. Only the most recent attempt submitted by each learner is included inthe count. For example, consider a dropdown problem that has five possibleanswers. The report or file contains up to five rows, one for each answersubmitted by at least one learner in their last attempt to answer the problem.

If the problem that you select includes more than one part, the chart andreport for the first part appears. To select a different part, you use theSubmissions for Part number drop-down.

For problems that use the Randomization feature in Studio, the report hasone row for each problem-variant-answer combination selected by at least onelearner. For more information about this randomization option, seeRandomization.

Content

The course will provide an introduction to modern cryptography. We will cover many practical topics, such as how to correctly use block ciphers and hash functions for the most common tasks: encryption and message authentication. In addition, with what time we remains, we will also cover several recent topics in cryptography, such as the use of block chains for crypto currencies, data sanitization through differential privacy, and searching encrypted databases.

Objectives

The main objectives are to convey the importance of provable security, to teach students how to use cryptographic tools in a way that is provably secure, to provide students with the ability to decide whether a protocol is secure, and to demonstrate the range of what can be achieved with provable security.

Prerequisites

There are no formal prerequisites for this course, and I intend for everything to be self-contained. However, students should have some level of mathematical maturity. Accordingly, a course such as CS600 would be a good course to take prior to this one. Students should be comfortable proving that one computational task reduces to another (in a formal way), and they should have comfort with basic probability theory.

There will be 6 homework assignments, due every other week. Students are welcome to work in groups, but every student must write their solutions independently. Homework that appear overly similar will be considered to violate the honor code. Students may re-submit up to 3 homework assignments for re-grading. The intent is to encourage students to revisit material that they did not understand; students are discouraged from re-submitting homework to save a few points. Accordingly, the following rules apply:

a) Points earned on re-submissions will be earned at 80% value: if you lost 5 points on the first submission, you can earn back at most 4.

b) Before resubmitting a homework, you must attend office hours to discuss what you didn't understand.

c) Re-submissions are due two weeks after the graded homework was originally returned to the student.

d) Anything submitted for re-grading must be accompanied by the original submission.

I encourage students to type their answers, both because they will be easier to read, and also because I believe it helps you clarify your own thinking. You can use this LaTex template file, if it is helpful to you. There are also command definitions that might be helpful to you here. (If you're using the template file, you will need to remove the comment where the preamble file is included.) This is a great LaTex reference, with a list of useful symbols on page 75.

R is a language and environment for statistical computing and graphics. R provides a wide variety of statistical and graphical techniques, and is highly extensible. Basically, anything you could ever want to do using statistics has already been done in R.

Better yet R is completely free to use and download. Unfortunately, R has a bit of a learning curve to get comfortable using it. We will only be using a little bit of the whole power of R in our class, and I will introduce all the commands you will need as we come to them. You are authorized to use R for any homework questions and it will be available to you for any class requirements. R is the principle tool for completing the projects for the class.

As a little motivation the average salary of those who write computer code in R is over $100,000 a year. So learning a little bit of R may make you rich someday. It will also give you a leg-up over any future job market competitors, as knowledge of R is highly desirable by employers.

The true power of R lies in the harnessing of the work of millions of nerds across the globe who use R and write up useful packages which add new features to R. There are thousands of R packages which can be installed to add features to R, we will only be using a few of these in the class.

In particular, your instructor is a nerd who has created his own R package specifically for this class. You will be using this package almost every time we use R in this class. I will expect that you have loaded R Studio and have run the command library(HannayIntroStats) when giving directions in class, on tests, etc. Make sure you have installed my package and load it anytime you are working in this class.

If you want to change the type of a variable you can use the as.numeric, as.character, as.integer, etc functions. For example, if we want to store age as a integer instead as a numeric type we could use:

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