This post is intended to give everyone an overview of the midterm exam, to highlight the areas that were done well and to indicate areas that need work. I will also highlight questions that were similar to clicker questions used in classroom quizzes. The information is presented in the same order that the exam was set up.
Midterm mark distribution
First of all, the overall distribution of marks is presented in Figure 1. Although, the majority of students passed the midterm, 23 students out of 60 had marks 50% and lower and only two students out of 60 had a mark above 81%. The class average was 58%.
 |
| Figure 1. Distribution of marks for the SLSC 240 midterm. Percentage of students is out of 60 students and the midterm exam percent ranges are out of a total of 55 marks. |
Part I. Multiple choice questions
Overall, most students did relatively well on the multiple choice section. The average mark was 7.7 correct answers out of 10 possible marks. There were four questions that people struggled with though, these included questions b, e, g and h. At least 30% of the class selected the incorrect answer for these four questions.
The correct answer for b is 3 “soil forming factors are not expressed equally in all parts of the profile”.
Question e was actually a question that was previously used in a clicker quiz. The question appeared in exact same form, but on the midterm 37% of the class selected the incorrect answer. The correct answer for e is 3 “air filled porosity”.
The correct answer for g is 4 “the weight of soil/unit volume of soil solids”.
The correct answer for h is 1 “Aluminum Al3+”.
On the positive side, question c was very similar to a clicker question presented on CEC and 97% of the class got it correct. As well, question f (pH values) was very similar to a clicker question presented in class, but the pH values had been changed slightly and 75% of the class selected the correct answer, option 5.
Did you find the multiple choice questions difficult? Do you think the clicker quizzes prepared you for the type of questions you saw on the midterm?
Part II. Matching
Again, for the most part, the matching part of the exam was done relatively well. On average, students got 7.1 marks out of a possible 10. There were three terms that stood out as being difficult concepts. Soil dispersion, negative charge, and exchangeable H+ were terms that 50% or more the class matched incorrectly. These are all concepts associated with cation exchange capacity. In regards to negative charge, some of the problem may have been that half of the answer “isomorphous substitution” didn’t show up on the exam. However, it appears as though, CEC is still an area that people are struggling with.
Do you find cation exchange capacity a topic that is difficult to understand?
Part III. Short answer and calculations
Questions 3 and 5 were calculation questions. These questions were typically done relatively well; however, there were some clear problems with both calculations. Units, units, units. Almost everyone who knew how to do the calculations in question 3 forgot to put the answer in kg/hectare furrow slice. Almost 50% of the class got 2.5 out of 3 on this question because they forgot the correct units. Question 5 was similar too, a lot of people forgot to express the answer in cm3.
Another issue encountered was converting units. It’s always a good idea to double check the number of zeros you have when dealing with metric conversions. As well, if you aren’t sure how to proceed on a calculation question, it’s a good idea to try to draw the dimensions out or at least try something. Many students left question 5 completely empty and that meant losing 4 possible marks.
Bulk density. This is a concept that has been stressed in class a lot and several clicker questions have focused on bulk density. The majority of students were on the right track when it came to question 4, but just needed to fill out their answer. The average mark was 1.6 out of 3 possible marks for that question.
Part IV. Short answer (Question 6-8)
This is where the midterm started to go quite poorly for most people. For questions 6 to 8, the average mark out of 5 was less than 2.5. This is an area where people lost a lot of marks. The majority of marks lost were due to lack of information provided. In general, one sentence is not a sufficient answer for 5 marks. Individuals who used point form typically did better because they usually had 4 or 5 points listed. The basis for the answers for each of these three questions comes directly from the class notes.
Question 6.
Briefly explain how topography can influence the soil formation process.
 |
| These two slides are directly out of the topography lecture notes. |
Question 7.
What was the last period of glaciation (Wisconsin period) such a fortunate event in Saskatchewan prehistory?
 |
| Slide is from the glaciation lecture. |
Question 8.
What is soil structure? What are the benefits of good soil structure?
 |
| Last two slides from the soil structure lecture |
On questions 6, 7, and 8, students averaged approximately 7 marks out of a possible 15. This was a huge loss of marks for most people, especially when the exam was only out of 55 marks.
Part V. Long answer
The long answer question was quite interesting because 40 students out of 60 selected Option A, probably thinking it would be simpler. However, in terms of clicker questions presented in class, 3 questions provided the direct basis for the answer of Option B and only 1 clicker question dealt with Option A.
Option A.
The clicker question presented on this topic was, which soil genesis process does water NOT participate in?
-physical weathering
-chemical weathering
-biological weathering
-leaching
-parent material deposition
There was no correct answer for this question because water participates in all the processes listed. For full marks, you could have listed the 5 processes and briefly described each one. The average mark was 5.1 out of 10 for Option A.
Option B.
For the 20 brave souls in the class who attempted this option, there were plenty of hints dropped in the clicker quizzes.
Clicker question 1 on CEC
Which soil characteristic does CEC not influence?
-soil fertility
-soil moisture
-soil texture (correct answer, CEC does not influence texture, but texture DOES influence CEC)
-soil structure
-soil pH
Clicker question 2 on CEC
What soil property is NOT influenced by the negative charge on clay and organic matter (CEC)?
-soil fertility
-soil water holding capacity
-soil pH
-soil structure
-soil temperature (correct answer)
Clicker question 3 on CEC
A soil with a high cation exchange capacity will have
-a high clay content
-ability to resist leaching loss of cations from soil
-ability to supply more nutrient elements to plants
-all of the above (correct answer)
The correct answer for Option B could have included listing soil fertility, soil moisture/water holding capacity, pH, soil structure, etc. and briefly describing how they are affected by CEC. The average mark for Option B was 4.5 out of 10 but that is hard to compare to Option A because so few people even selected Option B.
Overall impressions and suggestions
I’ve included a few suggestions for writing exams just based on what I saw in the results from the midterm.
1. Take the time to write down anything you can think of for a topic, you never know, you might get partial marks.
2. If it takes you a long time to write, start with the long answer questions and leave the multiple choice and matching to the end because they go faster.
3. If a question is worth 10 marks, chances are you need to list 10 things or list 5 things and describe each item in some detail.
5. When studying, try to focus on topics that are stressed repeatedly in class, guaranteed they will show up on an exam in some form (most likely a long answer).
Did you find the clicker questions or the blog helped provide information or hints as to what would be on the midterm?
No comments:
Post a Comment