[Year 12 IT Apps] information needed for gantt charts

[Timmer-Arends]

Sorry about this, but the teacher in me couldn't let the quotes I wrote 
about this earlier go without translating it into something students could 
digest, and here is what it came up with:

Lead and Lag times are both enforced delays; that is, there is something in 
the nature of a task that forces a delay that the project planner must take 
into account.
The distinction is this:
If task B is dependent on task A and B cannot begin immediately after the 
completion of A, then the delay is called:
a Lead if it is caused by B
a Lag if it is caused by A

In contrast, Slack and Float are both artifacts of the project planning 
process:
If task B is dependent on A and we are  unsure of how long A will take, then 
we may choose to schedule B at a later start time so as to allow for a later 
than expected completion of A. In other words, we build some Slack into task 
A.

While Float occurs between parallel sequences feeding into a common 
dependency:
If C is dependent on both A and B, but A and B can be run in parallel, then 
the Float is the difference in time between A and B (the path on which there 
is no float is the critical path).

Pictures would be very useful at this point.

Regards
Robert T-A
Brighton SC


----- Original Message ----- 
From: "Mark Kelly" <kel at mckinnonsc.vic.edu.au>
To: "Year 12 IT Applications Teachers' Mailing List" 
<itapps at edulists.com.au>
Sent: Friday, March 06, 2009 8:23 AM
Subject: Re: [Year 12 IT Apps] information needed for gantt charts


I've always read that slack = float.

Timmer-Arends wrote:
> Since everybody else is having a go....
>  "A lead is a forced wait before a task can commence; eg scheduling a Post 
> Implementation Review on a project for two weeks after the installation 
> date. There may be no intervening activity planned, but we have to wait 
> anyway"
>  "A lag is a forced wait after an activity before an event can occur; eg 
> you might throw a concrete floor and then have to wait three days for it 
> to cure before laying it with tiles"
>  "the slack time for an event is given by subtracting its earliest time 
> from its latest time. This is a measure of the delay which the event could 
> suffer ...and still allow the project to finish within the original 
> estimate range"
>  "The float time is the amount of time that a task start could be delayed 
> without affecting the date upon which the succeeding event would occur
>  "Managing Information Technology Projects", McLeod and Smith (University 
> of Cape Town), Course Technology, 1996
>  ...and then there is the question of how deeply does one have to go into 
> all of this anyway?
>  Regards
> Robert T-A
> Brighton SC
>  ----- Original Message -----
>
>     *From:* PARAGREEN, Chris <mailto:Chris.PARAGREEN at kew.vic.edu.au>
>     *To:* Year 12 IT Applications Teachers' Mailing List
>     <mailto:itapps at edulists.com.au>
>     *Sent:* Thursday, March 05, 2009 12:36 PM
>     *Subject:* RE: [Year 12 IT Apps] information needed for gantt charts
>
>     My first post as a newbie IT teacher!
>
>
>     “Just” a question about some of the definitions for Gantt charts….
>
>     According to Potts (p30), lead time is, “… time leading up to or
>     before a task.” It further explains the concept, but essentially
>     this is it.
>
>     My understanding is that lead time is the time available to begin a
>     dependant task before its predecessor is finished.
>
>     For example, you can’t set up a computer until the box has arrived,
>     but you can prepare the room in advance.
>
>
>     Similarly, Potts states that slack time and lag time are the same
>     thing, whereas I think they are not.
>
>     Slack is the available time to allow for delays, but lag is the time
>     between when a task finishes and when it’s dependant task can begin.
>
>     For example, if pouring concrete, the actually pouring task might
>     have finished, but you have to wait for the concrete to cure (the
>     lag time) before you can paint it.
>
>
>     Are my definitions too precise for what we need to teach, am I
>     wrong, or am I missing something?
>
>
>     Regards,
>
>
>
>     Chris Paragreen
>


-- 
Mark Kelly
Manager - Information Systems
McKinnon Secondary College
McKinnon Rd McKinnon 3204, Victoria, Australia
Direct line / Voicemail: 8520 9085
School Phone +613 8520 9000
School Fax +613 9578 9253
kel at mckinnonsc.vic.edu.au

Webmaster - http://www.mckinnonsc.vic.edu.au
IT Lecture notes: http://vceit.com
Moderator: IT Applications Mailing List

RealMenDon'tNeedSpacebars.

_______________________________________________
http://www.edulists.com.au - FAQ, resources, subscribe, unsubscribe
IT Applications Mailing List kindly supported by
http://www.vcaa.vic.edu.au/vce/studies/infotech/itapplications3-4.html - 
Victorian Curriculum and Assessment Authority and
http://www.vitta.org.au  - VITTA Victorian Information Technology Teachers 
Association Inc