Statistics window

The statistics windows, Statistics and Element data can most conveniently be viewed by pressing F5 (or choosing Window : Layout : Apply Layout : Classic). This arranges the statistics windows in the classic shape first introduced in SuperMemo 3.0 (1988):

Learning parameters displayed in the statistics window:
  • Date - current date and the day of the week. If this value is preceded with Night, it means that the new day has already started but the old repetition day will last as many hours past midnight as defined in Midnight clock shift. In the example, the collection is being used on Friday, August 27, 1999
  • First day - date on which the learning process began in the given collection. The collection has been in use since December 15, 1987 (i.e. the birth date of SuperMemo as software)
  • Day - number of days in the learning process (i.e. number of days between Date and First day).
    Day = Date - First day The presented collection has been in use for 4274 days (i.e. nearly 12 years)
  • Total - total number of items, topics and tasks in the collection.
    Deleted elements do not contribute to the total count of elements in the system. In the example, the collection comprises nearly 70,000 elements
  • Memorized - total number of items introduced into the learning process with options such as Learn or Remember. If an item takes part in repetitions it is a memorized item. The presented collection has nearly 56 thousand of elements in the learning process and these elements make up 88.8% of the entire collection, i.e. Memorized/Total=0.888
  • Memorized/Day - number of elements memorized in the collection per day. In the example, the average of 13 elements has been memorized in the presented collection over the last 12 years
  • Pending - total number of elements (topics or items, but not tasks!) that have not yet been introduced into the learning process but still away memorization with Learn, Remember, etc. All pending elements are kept in the so-called pending queue that determines the sequence of learning new elements. Dismissed items are not kept in the pending queue. In the example, the collection contains 7007 elements that can still be memorized
  • Dismissed - total number of elements (topics, items or tasks) that have been excluded from the learning process and are kept only as reference material or tasklist material. Dismissed items are neither pending nor memorized. All topics that are stored in the pending queue are dismissed automatically after the first presentation (see: Topics vs. items). All tasks are dismissed by default, i.e. they never take part in repetitions. In the example, nearly five thousand element have been dismissed, used as element folders or used as tasks (e.g. as reading list positions)
  • Outstanding - number of outstanding items scheduled for repetition on a given day. The first number (before the plus sign) indicates the number of items scheduled for this given day and not yet processed. The second number (after the plus sign) indicates number of items that have already been repeated today but scored less than Good (4). Those are the items that make up the final drill queue. In the presented collection, there are still 138 elements that have not and should be repeated on August 27, 1999. Of previously repeated elements (on Aug 27 or before), 75 have scored less than Good and have not yet been removed from the final drill queue by scoring Good or Bright
  • Retention - estimated knowledge retention in the opened collection. In the example, nearly 95% of the material should be recalled in a random test on all elements in the collection (you can test your retention using random tests and see if SuperMemo's estimation is accurate)
  • Measured FI - the value of forgetting index as measured at repetitions, i.e. the actual proportion of items not remembered at the moment of repetitions. The number in parentheses indicates Measured FI for the current session. It is quite usual to have Measured FI higher than Average FI. This is due to two factors: (1) no learning process is perfect, and every user will experience delays in repetitions from time to time, (2) SuperMemo imposes some constraints on the length of intervals that make it sometimes schedule repetitions later than it would be implied by the forgetting index. The constraints in computing intervals, for example, prevent the new interval to be shorted than the old interval (except for the situation in which the item has been forgotten). For low values of forgetting index and items with low A-Factor, the new interval might often be shorted than the old one! In the presented example, 10.28% of repetitions end with grades less than Pass. In the current session on Aug 27, 7.1% of memory lapses have been recorded in repetitions
  • Average FI - average forgetting index which says what is the average value of the forgetting index in the entire collection (the number in parentheses is the default forgetting index). If forgetting index of individual elements is not changed manually, Average FI is equal to the default forgetting index as set in Tools : Options : Learning : Forgetting index. The default forgetting index is the requested forgetting index given to all new elements added to the collection. Forgetting index, in general, is the proportion of items that are not remembered during repetitions. The lower the value of the forgetting index the better the element is remembered but the more repetitions will be needed to keep it in memory. Optimum value of the forgetting index falls into the range from 7% to 13%. Too low forgetting index makes learning too tiresome due to a prohibitively large number of repetitions. All elements can have their desired forgetting index set individually. The easiest way to change the forgetting index of a large number of elements is to use Forgetting index option on the pop-up menu in the contents window. In the presented example, the average forgetting index is 10.2% while the default forgetting index is 10%. See: Using forgetting index
  • Burden - average number of repetitions per day. This value is equal to the sum of all inverse intervals (i.e. 1/interval). The interpretation of this number is as follows: every item with interval of 100 days is on average repeated 1/100 times per day. Thus the sum of inverse intervals is a good indicator of the total repetition workload in the collection. The presented collection requires about 185 repetitions per day
  • Burden +/- - the change of the Burden parameter above in the present session. Here, on Aug 27, the average number of repetitions increased by half an item per day
  • Workload - the average daily time used for responding to questions in a given collection.
    Workload = Burden*Avg. time. In the presented collection, 185 repetitions per day take 8.3 seconds each which results in a daily repetition time of over 25 minutes. Note that this is only the time it takes to answer question. A usual session may be twice longer due to grading, editing, reviewing the collection and plain interruptions
  • Speed - the average knowledge acquisition rate, i.e. the number of items memorized per year per minute of daily work. Initially this value may be as high as 100,000 items/year/minute (esp. if you enthusiastically start working with the program before truly measuring its limitations -- or rather the limitations of your memory); however, it should with time stabilize between 50 and 400 items/year/minute. In the presented collection, every minute of work per day results in 185 new items memorized each year
  • Cost - total time cost of memorizing a single item, i.e. total learning time divided by the number of memorized items. Cost = Total time / Memorized
    In the presented example, the total repetition time per single item is 2.5 minutes. In other words, each item has contributed 2.5 minutes to the total of non-stop 97 days and 4 hours of repetitions
  • Daily cost - daily repetition time per each newly memorized item.
    Daily cost = Workload / (Memorized/Day)
    In the presented collection, each of the 13 newly memorized items per day contributes about 1.97 minutes of repetitions to the total workload of 25.75 minutes per day
  • Repetitions - average number of repetitions per memorized item in the collection. Here an average item has been repeated 6.5 times
  • Interval - average interval of memorized items in the collection. Here an average memorized items has already reached the average interval of 1372 days or nearly four years
  • Lapses - average number of times individual elements have been forgotten in the collection (only memorized elements are averaged). The number in parentheses shows the number of lapses in the current session. Here an average element has been forgotten about once. In the presented session, only one lapse has occurred
  • Last Rep - average date of the last repetition among memorized items in the collection. Here the average date of the last repetition falls on January 10, 1998
  • Next Rep - average date of the next repetition among memorized items in the collection.
    Next Rep = Last Rep + Interval
    Here the average date of the next repetition is October 13, 2001 or 1372 after Jan 10, 1998
  • Completion - the expected date on which all elements from the pending queue will be memorized assuming the present rate of learning new items.
    In the example, it would take until February 15, 2001 to memorize all 7007 pending items at the speed of 13.04 items per day (beginning with Aug 27, 1999)
  • Time - total response time in the current session and the total session time (in parentheses). Here the total time needed to respond to questions in the current sessions was 2 minutes and 42 seconds in a session that has lasted 7 minutes and 20 seconds. Such significant differences in time occur when the collection is intensely edited or restructured
  • Total time - total time taken by responding to questions in the collection. This time can only be roughly estimated for collections created with SuperMemo 98 or with earlier versions of SuperMemo. The exact measurements of this parameters are only made as of SuperMemo 99. If you upgrade your collections to SuperMemo 99, SuperMemo will assist you in estimating this number. Either you have to provide the average time you have spent on repetitions per day (until the day of upgrade) or SuperMemo will derive this time from the total number of items, average number of repetitions, average number of lapses and the average repetition time. In the presented example, answering questions during repetitions took over 97 days non-stop (in twelve years of repetitions)
  • Avg. time - average response time in seconds (i.e. the time between displaying the question and choosing Show answer or equivalent). In the presented collection, the average time to answer a single question is 8.3 seconds 
  • Rep count - the total count of repetitions made in the collection. In the presented collection, 606 thousands repetitions have been made. This is about 10 repetitions per memorized item (this count includes repetitions of items that have been reset, forgotten, dismissed, deleted, etc.)
  • A-Factor - average value of A-Factor among memorized items in the collection. A-Factor is a measure of item difficulty. The higher the A-Factor, the easier the item. In the presented collection, the average A-Factor is about 4.09. This indicates that the collection is rather well-structured and the material is thus relatively easy to remember
  • Subset/Test - number of items in the random test queue (used when running random tests with Tools : Random tests) or number of outstanding items (used when making repetitions in a single branch with Contents : Learn). In the case of learning with Contents : Learn, the number of outstanding items and the number of pending items are displayed and separated by the plus sign. Here the lone symbol "-" indicates that neither random test nor branch learning are being executed


  1. Items are added to the final drill not only during standard repetitions when you grade an element below Good (4). Operations such as Remember (Ctrl+M), Remember Cloze, and Add to drill (Shift+Ctrl+D) will also extend the final drill queue
  2. Some fields of the statistics window can be edited. For example: Measured FI, Total time, Rep count, etc. To edit and entry, click it, type the new value and press Enter. If the entry cannot modify SuperMemo will warn. For example: Retention entry cannot be modified
  3. See Survey 1994 and Survey 1999 for some interesting notes about the speed of learning reached with SuperMemo