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

Item parameters displayed in the Item data window

Date - current date

First day - date on which the learning process began in the given knowledge system

Day - number of days in the learning process (i.e. number of days between Date and First day)

Memorized - total number of items introduced into the learning process with options such as Learn or Commit. If an item takes part in repetitions it is a memorized item

Pending - total number of elements (i.e. topics or items) that have not been yet introduced into the learning process but still away memorization with Learn, Learn : New material, Commit, etc. All pending items are kept in the so-called pending queue that determines the sequence of learning new items. Dismissed items are not present in the pending queue.

Dismissed - total number of elements (i.e. topics or items) that have been excluded from the learning process and are kept only as reference material. Dismissed items are neither pending nor memorized. All topics that are stored in the pending queue are dismissed automatically after the first presentation.

Total - Total number of topics and items in the knowledge system. It is worth noting that Memorized+Pending+Dismissed=Total. Deleted elements do not contribute to the total count of elements in the system.

Outstanding 0+0 - number of outstanding items schedule 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.

Default FI - default forgetting index given to all new elements added to the system. Forgetting index, in genera, 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 afforded to it. 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. By default all elements receive initially the forgetting index equal to Default FI. 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

Average FI - average forgetting index which says what is the average value of the forgetting index in the entire knowledge system. If forgetting index of individual elements is not changed manually, Average FI is equal to Default FI.

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. It is quite normal 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!

Burden - average number of repetitions per day. This value is equal the sum of all inverse intervals (i.e. 1/interval). The interpretation of this approach 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 knowledge system.

Repetitions - average number of repetitions per memorized item in the knowledge system.

Lapses - average number of times individual items have been forgotten in the knowledge system (only memorized items are averaged).

Interval - average interval of memorized items in the knowledge system.

A-Factor - average value of A-Factor among memorized items in the knowledge system. A-Factor is a measure of item difficulty. The higher the A-Factor, the easier the item.

Last Rep - average date of the last repetition among memorized items in the knowledge system.

Next Rep - average date of the next repetition among memorized items in the knowledge system.

Test - number of items in the random test queue (used only at running random tests from Tools : Random tests)

Item parameters displayed in the Item data window

Repetitions - number of repetitions afforded the item whose data is being displayed. If the item had been forgotten, the number of memory lapses is displayed in parentheses.

Interval - current interval of the item, i.e. the number of days between Last repetition and Next repetition.

Last repetition - date of the last repetition of the item.

Next repetition - date on which the next repetition of the item should take place.

A-Factor - A-Factor associated with the item. A-Factor is the measure of item difficulty. The higher the A-Factor, the easier the item. The most difficult items have A-Factor equal to 1.3.

U-Factor - quotient of the old interval and the new interval. Only in items that have been repeated only once, U-Factor equals the first interval. U-Factors makes up an important element of the Algorithm SM-8. If you do not know the algorithm, U-
Factor does not have much meaning to you.

Forgetting index - planned probability of forgetting the item in the next repetition (in percent). Forgetting index can be changed to a desired value (e.g. with Forgetting index on the pop-up menu in the Contents window). For example, if the forgetting index is 10%, you stand a 90% chance that you will remember the item in the next repetition.

Future repetitions - estimated number of repetitions of the item in the next thirty years. This value is easily derived from A-Factor, Repetitions and the matrix of optimal factors (see Algorithms SM-8).

First grade - grade obtained by the item in its first repetition. This value is important as the first grade vs A-Factor correlation is used to quickly determined A-Factor of items right after their first repetition.

Ordinal - ordinal number associated with the item. Ordinals can be used to sort items in the pending queue, final drill queue, etc. The lower the ordinal, the higher the priority of the item. Ordinals range from 0 to 100.

Type - type of the element: item or topic.

Status - current status of the element: dismissed, pending or memorized.

Repetition parameters displayed in the Item data window

To understand repetition parameters you should have a rudimentary knowledge of Algorithm SM-8.

Repetitions- number of repetitions afforded the item whose data is being displayed (after the current repetition). If the item had been forgotten, the number of memory lapses is displayed after the colon. The number in the parentheses indicates the number of repetitions that the item would need to reach its current interval assuming the current value of the matrix of optimal factors and no memory lapses on the way. This hypothetical value is indeed used to index the matrix of optimal factors and the matrix of retention factors in computing the new values of individual entries at repetitions.

Optimum interval - optimum interval the item should use to ensure the forgetting probability determined by Forgetting index.

New interval - new interval given the item. New interval might optimally be equal to Optimal interval; however, two factors may make these two values differ: (1) minor interval dispersion is needed to avoid scheduling a large number on the same day (interval dispersion also speeds up the convergence of the optimization algorithm), and (2) some constraints imposed on the new interval may make it impossible for it to equal Optimum interval. For example, the new interval cannot be shorter than the old interval (Interval). For low forgetting index, it is quite common for Optimal interval to be shorter than Interval.

Next repetition - date on which the next repetition should take place (after the current repetition).

New A-Factor - new value of A-Factor estimated for the item after the repetition.

New U-Factor - new value of U-Factor (i.e. the quotient of the new interval and the old interval; see U-Factor above for more)

Expected FI - see the description of the Algorithm SM-8.

Estimated FI - see the description of the Algorithm SM-8.

Normalized grade - grade normalized for the same A-Factor and the same forgetting index.

R-Factor change - change of the R-Factor corresponding to the current repetition number (the one displayed in parentheses at Repetition) and A-Factor (displayed at A-Factor among Item parameters described earlier).

O-Factor change - change of the O-Factor corresponding to the current repetition number (the one displayed in parentheses at Repetition) and A-Factor (displayed at A-Factor among Item parameters described earlier).

Cases - number of repetition cases used to compute the values of O-Factor and R-Factor corresponding to the current repetition number (the one displayed in parentheses at Repetition) and A-Factor (at A-Factor in previous column).

Status bar - the status bar displays some information available from the Statistics window in a concise and graphic way. The first field shows Memorized/(Memorized+Pending). In other words, it shows what proportion of pending items have already been memorized. The second field shows Outstanding/(maximum Outstanding). It illustrates how many items of the current day have yet to be repeated (before the plus sign) or have to be rehearsed in the final drill (after the plus sign). The progress bar displays the same information in the graphic form. The blue color shows the proportion of items passed successfully (i.e. with the grade Bright (5) or Good (4)). The red color shows the proportion of items passed with the grade less than Good (4). And the white color shows the proportion of items that have not yet been passed.

The right part of the status bar is used to display hints for menu items, buttons, statistical parameters, etc. As you have probably noticed, this part becomes yellow as soon as the mouse pointer moves over a screen component that has a unique function in SuperMemo.