core_question\statistics\questions\calculated_for_subquestion Class Reference

A class to store calculated stats for a sub question. More...

Inheritance diagram for core_question\statistics\questions\calculated_for_subquestion:

Public Member Functions
	__construct ($step=null, $variant=null)
	Constructor.
	break_down_by_variant ()
	Do we break down the stats for this question by variant or not?
	cache ($qubaids, $timemodified=null)
	Cache calculated stats stored in this object in 'question_statistics' table.
	clear_variants ()
	Delete the data structure for storing variant stats.
	get_sub_question_ids ()
	Get any sub question ids for this question.
	get_variants ()
	Array of variants that have appeared in the attempt data for this question.
	populate_from_record ($record)
	Load properties of this class from db record.
	random_selector_string ()
	Used to determine which random questions pull sub questions from the same pools.
	sort_variants ()
	Sort the variants of this question by variant number.

Public Attributes
	$covariance
	$covariancemax
	$covariancemaxsum = 0
	$covariancesum = 0
	$covariancewithoverallmark
	$covariancewithoverallmarksum = 0
bool	$differentweights = false
	Have the slots this sub question has been used in got different grades?
float	$discriminationindex
float	$discriminativeefficiency
float	$effectiveweight
	effective weight of this question.
float	$facility
	$markarray = array()
	$markaverage
	$markvariance
	$markvariancesum = 0
float	$maxmark
	max mark achievable for this question.
string	$minmedianmaxnotice = ''
	if this stat has been picked as a min, median or maximum facility value then this string says which stat this is.
	$negcovar = 0
	$othermarkaverage
	$othermarksarray = array()
	$othermarkvariance
	$othermarkvariancesum = 0
string	$positions
	comma separated list of the positions in which this question appears.
object	$question
	full question data
	$questionid
null float	$randomguessscore = null
	The average score that students would have got by guessing randomly.
int	$s = 0
	total attempts at this question.
float	$sd
	standard deviation
	$slot = null
int	$subqdisplayorder
	only set immediately before display in the table.
	$subquestion = true
	$subquestions = ''
float	$summarksaverage
	The average for all attempts, of the sum of the marks for all positions in which this item appeared.
integer	$timemodified
	Set if this record has been retrieved from cache.
	$totalmarks = 0
	$totalothermarks = 0
float	$totalsummarks = 0
	The total of marks achieved for all positions in all attempts where this item was seen.
array	$usedin = array()
	What slots is this sub question used in?
null integer	$variant = null
	if this property is not null then this is the stats for a variant of a question or when inherited by calculated_for_subquestion and not null then this is the stats for a variant of a sub question.
calculated[]	$variantstats = array()
	An array of calculated stats for each variant of the question.

Protected Attributes
	$fieldsindb

Detailed Description

A class to store calculated stats for a sub question.

Copyright

2013 The Open University

Author

James Pratt me@ja.nosp@m.miep.nosp@m..org

License

http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

Constructor & Destructor Documentation

__construct()

core_question\statistics\questions\calculated_for_subquestion::__construct	(		$step = null,
			$variant = null )

Constructor.

Parameters

object | null	$step	the step data for the step that this sub-question was first encountered in.
int | null	$variant	the variant no

Member Function Documentation

break_down_by_variant()

core_question\statistics\questions\calculated::break_down_by_variant ( )

inherited

Do we break down the stats for this question by variant or not?

Return values

bool

Do we?

Reimplemented in core_question\statistics\questions\calculated_question_summary.

cache()

core_question\statistics\questions\calculated::cache ( $qubaids, $timemodified = null )

inherited

Cache calculated stats stored in this object in 'question_statistics' table.

Parameters

qubaid_condition	$qubaids
int | null	$timemodified	the modified time to store. Defaults to the current time.

get_sub_question_ids()

core_question\statistics\questions\calculated::get_sub_question_ids ( )

inherited

Get any sub question ids for this question.

Return values

int[]

array of sub-question ids or empty array if there are none.

get_variants()

core_question\statistics\questions\calculated::get_variants ( )

inherited

Array of variants that have appeared in the attempt data for this question.

Or an empty array if there is only one variant.

Return values

int[]

the variant nos.

populate_from_record()

core_question\statistics\questions\calculated::populate_from_record ( $record )

inherited

Load properties of this class from db record.

Parameters

object

$record

Given a record from 'question_statistics' copy stats from record to properties.

random_selector_string()

core_question\statistics\questions\calculated::random_selector_string ( )

inherited

Used to determine which random questions pull sub questions from the same pools.

Where pool means category and possibly all the sub categories of that category.

Return values

null|string

represents the pool of questions from which this question draws if it is random, or null if not.

Member Data Documentation

$fieldsindb

core_question\statistics\questions\calculated::$fieldsindb

protectedinherited

Initial value:

= array('questionid', 'slot', 'subquestion', 's', 'effectiveweight', 'negcovar', 'discriminationindex',
        'discriminativeefficiency', 'sd', 'facility', 'subquestions', 'maxmark', 'positions', 'randomguessscore', 'variant')

$minmedianmaxnotice

string core_question\statistics\questions\calculated::$minmedianmaxnotice = ''

inherited

if this stat has been picked as a min, median or maximum facility value then this string says which stat this is.

Prepended to question name for display.

$randomguessscore

null float core_question\statistics\questions\calculated::$randomguessscore = null

inherited

The average score that students would have got by guessing randomly.

Or null if not calculable.

$subqdisplayorder

int core_question\statistics\questions\calculated_for_subquestion::$subqdisplayorder

only set immediately before display in the table.

The order of display in the table.

$timemodified

integer core_question\statistics\questions\calculated::$timemodified

inherited

Set if this record has been retrieved from cache.

This is the time that the statistics were calculated.

$variantstats

calculated [] core_question\statistics\questions\calculated::$variantstats = array()

inherited

An array of calculated stats for each variant of the question.

Even when there is just one variant we still calculate this data as there is no way to know if there are variants before we have finished going through the attempt data one time.

$variants

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The documentation for this class was generated from the following file:

• question/classes/statistics/questions/calculated_for_subquestion.php