Quiz score and time spent on quiz

I am disappointed at how my students are doing on their reading quizzes this semester. I use the quizzes to motivate them to get the reading done before we meet in class, as I want them to have a broad familiarity with the chapter before I lecture or we do a group activity or watch a video that is more focused. Each quiz has 10 questions that I wrote, and I tried to make some questions easy and some questions that required some critical thinking.

The average score did not change when I increased the time limit after the first three quizzes:

Quiz	Time Limit	Attempts	Average
1	10 mins.	31	62.9%
2	10 mins.	43	48.8%
3	10 mins.	41	47.8%
4	20 mins.	41	55.6%
5	20 mins.	37	56.8%
6	20 mins.	34	48.8%
7	20 mins.	35	54.6%

Quiz attempts with a 10-minute limit averaged 53.17% and those with a 20-minute limit averaged 53.95%.

Then I thought I might look at how much time each student spent on the quiz and see if I could correlate that with a score but I discovered nothing interesting there. I had to do some heavy data massaging (create a report in D2L that included the time per attempt and then use Word and Excel to strip out all of the questions and answers for each attempt), and I discovered the following for chapter 1:

Score	Count	Average Time
8	5	6.2 mins.
7	8	6 mins.
6	7	6.4 mins.
5	8	6.6 mins.

One student each scored 3 and 4 points on the quiz.