Saturday 27 December 2014

Bought myself a new DSLR camera

I bought my first DSLR camera (a Pentax *ist DS) more than a decade ago, and it produced nice quality images despite the limited 6MP image resolution. One nice aspect was that I could continue to use the old K-mount lenses I'd bought in the 80's to use with my previous Pentax SLR 35mm camera, although I had to focus and adjust exposure settings manually when using those lenses.

However, that old camera had developed an electrical fault (the inbuilt flash would strobe and cause the camera to shut down when you turned it on) and despite twice trying to have it fixed by the local authorized service center, the fault kept recurring, so I decided to finally buy a new camera.

My wife and sons all have compact digital cameras that take nice 'snapshot' photographs, but I still fancy myself as a bit of an amateur photographer, so I decided to buy a more expensive digital SLR camera. In the end I opted for the Nikon D3300 camera twin lens kit. It comes with 18-55mm and 55-200mm zoom lenses, and with the inbuilt lithium battery it only weighs about half my old Pentax DSLR that required four AA batteries. It's one of the cheaper DSLR Nikon cameras, but I don't need the features of the much more expensive 'professional' cameras, or even the 'bells and whistles' that come with models such as the D5300 (who really needs WiFi connectivity between their camera and tablet, or automatic geotagging? Especially when it costs an extra hundred bucks and doesn't improve the image quality one iota?).

I took a few test snapshots during a weekend away over Christmas, and will need to watch a couple of videos on how to use it properly before we go on a two week cruise around New Zealand next month (I didn't even change the settings from the default medium-res JPEG and AUTO mode during this first outing - although I did manage to drop the new camera in the dirt once when the neck strap came updone!). One good thing these days is that SD cards are so cheap that you can buy an 8GB SD card for about the same cost as a 24 exposure roll of 35mm print or slide film used to cost, and then simply save it as the backup media after downloading the contents of a full SD card onto your PC. Even when saving each 24MP exposure in both RAW and high resolution JPEG formats an 8GB SD card will hold around 180 exposures. I've bought a handful of SD cards to use during my holidays so I won't have to worry about downloading images during the trip.

SD cards are fairly robust (according to Digital Camera Shopper "The memory cards in most cameras are virtually indestructible.. Five memory card formats survived being boiled, trampled, washed and dunked in coffee or cola" but the digital data may only last 10-15 years in storage before a significant amount of corruption or data loss becomes apparent. So for true archival storage gold CD-R are probably more secure (whether or not any of my photos will be worth preservation is a separate issue!).

Ellenborough Falls, NSW. Copyright 2014.

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Tuesday 23 December 2014

Which Sydney Selective High School is 'best'?

While some parents apparently take the view that the 'best' selective high school is simply the one with the best HSC results (usually taken to be the % of their year 12 student cohort on the HSC DA list), this ignores the fact that the 'best' year 7 students will, generally speaking, go on to achieve the 'best' HSC results six years later. So the selective school with the highest Year 7 entry cut-off mark (James Ruse) will get the highest percentage of students making the 'distinguished achievers' list even if there was absolutely no difference in the quality of teaching etc. between the selective high schools. What is of more interest is whether or not there is a difference in how well individual selective high schools are helping each student achieve their 'personal best', based on their individual potential.

A more considered indicator of which selective high school is 'best' (in some sense) might therefore be which one 'value adds' the most during a student's secondary schooling? One way to measure this (that schools use internally, but few schools are game to make public) is how the NAPLAN results for a cohort change from Year 7 to Year 9, compared with the typical change for 'similar' schools. However, as NAPLAN testing stops in Year 9, a better indicator of a school's influence over the entire secondary school period might be to look at HSC outcomes (%DA) vs. the cut-off entry mark into Year 7 for the that cohort of students. While there is some movement of students between schools from Year 7 to Year 12, selective school students generally tend to stay at the school they gained entry to in Year 7, and the relatively small number of additional students admitted in Years 8-11 would probably be a similar standard to the general school population.

As the Year 7 entry cut-off marks for NSW selective high schools were only published from 2008 onwards, the HSC results from 2013 and 2014 can only now be used to plot the correlation between Yr 7 entry cut-off mark and the performance (in terms of %DA in the HSC) of that cohort when they reach Year 12. To date there are only two years data available (2008>2013, and 2009>2014), and it will be interesting to see if the trends apparent in this limited data set hold in future years. {update: see post with more recent data - here}

The results for thirteen NSW selective high schools that are generally ranked in the 'top ten' (in terms of entry cut-off mark) are plotted in figure 1 below. It can be seen that there is a clear correlation between the cut-off mark required for entry into each school and the percentage of these students that perform well enough to make the HSC 'distinguished achievers' list when they get to year 12. While some scatter is to be expected, the points above the trend line would suggest a school has 'added value', while those schools/years falling below the trend line appear to have under-performed in the HSC relative to the potential they exhibited going into Year 7.

The scatter show in figure 1 increases as entry cut-off decreases. This is to be expected as there is greater potential for year-to-year variation in the average ability of a cohort entering a school with a lower cut-off mark. While the cut-off mark might be the same in 2008 and 2009, the cohorts in a selective school with a lower cut-off mark could vary considerable if in one particular year a few more students with high selective school entry test scores choose to attend the 'lower' ranked school due to travel considerations etc. This wouldn't change the minimum entry score required to be accepted into the school, but could boost the % of students making the DA list.

Figure 2 shows the data grouped by gender segregation - the selective boys schools, the selective girls schools, and the selective co-ed schools. From this figure it appears that there is little impact of gender segregation in years 7-12 and student's HSC performance. The couple of data points for boys and co-ed selective schools that appear significantly below trend belong to three specific schools, so are more likely to be due to the schools 'value add' than to gender segregation effects. If that is the case, one wonders if it is such as good idea to segregate students on gender lines during high school. Getting them acclimated to interacting with the opposite sex during high school may be better than leaving it until the booze and party enhanced environment of your typical university campus!

Finally, figure 3 shows the data colour coded to each school. It appears (although it is hard to draw solid conclusions from only two data points) that some of these selective high schools (Girraween, Sydney Technical High School and Normanhurst) under-perform, while others (such as Manly Campus and North Sydney Boys) may out-perform. Such trends will become clearer as HSC results for 2015-2017 are published in future years. In the case of Sydney Technical High School the relative under-performance may simply be because students choosing to attend that school are more interested in technical subjects that do not 'scale' as well as some other HSC subjects (due to the general composition of students taking that subject across all NSW high schools).

It should be noted that these results are Sydney-centric, as there is a greater pool of students within reasonable traveling distance of the Sydney selective high schools, which pushes up their cut-off marks for entry. Selective high schools in country areas tend to be in lower demand, so their cut-off marks tend to be lower. This would mean there is more year-to-year variation in the average ability of the student cohort, independent of the cut-off mark, making it harder to tell if a particular school in these areas is performing above or below trend from the available data. Hopefully BOSTES uses their access to the median entry score of students in these schools and their eventual HSC results to identify which school are achieving the best outcomes, and identifying which variables (such as teacher qualifications, experience, school resources, student socio-economic background etc.) are important, and which positive factors can be promulgated to other schools.

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Sunday 21 December 2014

School reports hit the hip pocket

The school year has ended and the boys have been shipped off with my parents to spend a week at a beach-front resort on the mid-north coast before we join them on Christmas eve. The boys deserve a break - they've both been applying themselves at school and have achieved the results they deserve. They both got "straigh-A's" on their school report cards, so I'll be giving them $30 each as a small reward for their efforts. The rewards system I introduced last year was $5 for every 'A' (actually, the best report grades currently in use in the NSW education system are 'outstanding' in high school reports, and 'high' in primary school reports). But this year I simplified in to just being a flat $30 rewards for getting straight-A's.

DS1's school achieved another good outcome in this year's HSC results - ranking 8th in the state with 50.7% of the students making the 'distinguished achievers' list. But the whole idea of ranking high schools is a bit silly, as the results are fairly predictable and seem to be based mostly on the mix of students that are attending the school, rather than the 'value added' by the school itself.

For example, the school that is consistently ranked number one in the state, James Ruse High, is therefore the most sought-after school for selective school applicants. It therefore has the highest 'cut-off' mark of any of the selective high schools each year (ie. only the 'best' students can get in), and, as sure as night follows day, six years later that cohort of students gets the best HSC results in the state...

The correlation between the minimum entry score (or 'cut-off; mark) required to gain entry into a selective high school and its HSC results seems quite clear, so it will be interesting to see how DS1s school performs in future years. According to the trend in 'cut-off' mark over the past several years, I would predict that it will continue to do well (as the cut-off marks for entry into those years had increased by around 5 marks). Unfortunately entry cut-off marks have only been published since 2007, so the trend can't be quantified just yet, but should become clear over the next few years...

Manly Selective HS:
Yr 7 entry             >> HSC results
Year  cut-off              Year    Rank     %DA
2014   205                  2019
2013   207                  2018
2012   205                  2017
2011   201                  2016
2010   202                  2015
2009   199                  2014      8         50.7
2008   201                  2013      11       43.0
2007   n.a                   2012      7         51.4
2006   n.a                   2011      10       45.1
2005   n.a                   2010      7         47.2
2004   n.a                   2009      15       41.1
2003   n.a                   2008      15       37.7
2002   n.a                   2007      20       32.6

Comparing these to the data for one of the top selective schools (Sydney Boys High) shows that the Year 12 HSC results are dependent on the quality of the cohort selected for entry into Year 7:

Sydney Boys Selective HS:
Yr 7 entry             >> HSC results
Year  cut-off              Year    Rank     %DA
2014   218                  2019
2013   216                  2018
2012   222                  2017
2011   223                  2016
2010   219                  2015
2009   219                  2014      6         53.0
2008   219                  2013      7         48.2
2007   n.a                   2012      8         48.5
2006   n.a                   2011      4         56.7
2005   n.a                   2010      6         49.2
2004   n.a                   2009      7         43.8
2003   n.a                   2008      7         44.7
2002   n.a                   2007      10       39.2

Of course, the ranking of the school itself only has an indirect impact on an individual student's HSC result and ATAR (as the performance on the student cohort at a particular school in the HSC will affect the scaling of the HSC marks of students attending that school). Of more importance will be how well DS1 does in his chosen HSC courses, and where he ranks amongst fellow students at his school in these subjects. Getting an 'outstanding' result in all Yr 9 subjects, which puts him in the top half of the school in every subject, suggest he should be able to achieve an ATAR of 98+. But as he has no clear idea of which course he wants to do at university, it comes down to simply doing as well as he can, so that he has a good chance of gaining entry into whichever course he fancies.

DS1 is enrolled (via distance education) in an HSC preliminary subject (Software Design and Development) as an 'accelerated' student next year, so he will have completed one of his HSC subjects whilst he's still in Year 11. If he does well enough in that subject it may help him get a good ATAR result, as he will still be doing the normal workload of other HSC subjects in year 12, so he will have an extra couple of units to pick from when the best 10 units are used to calculate his ATAR. Of course the disadvantage of doing his favorite subject as an 'accelerated' student is that he will be competing with students that are a year ahead of him. Also, the distance education course is offered by a non-selective high school that doesn't have exceptional HSC results overall. So unless DS1 ranks at the very top of his class in SDD, his scaled mark in this subject won't be very high. Also, SDD in general doesn't scale up very much, due to the general caliber of the students taking this subject for the HSC, so it's unlikely his SDD result will be included in his 'best 10 units' used for ATAR calculations.

DS1 has also been offered a place in the UNSW High School Computing course in the first half of next year - which teaches the first year university course in computing to selected Yr 11/12 high school students (and a few 'exceptional' year 10 students, such as DS1). It should be fun for him to do, and quite exciting for him to be attending 'uni' after school once a week! While not an HSC subject (so I'm glad he is able to do it while in Year 10, so it won't impact on his Year 11/12 studies), it should help him do well in his SDD course. Also, if he does extremely well (getting 85%+) he would be allowed to enter the CSE Elite students program if he decides to enrol in computer science at UNSW.

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Sunday 7 December 2014

Net Worth: November 2014

Net Worth was down slightly during November, despite another monthly gain in the valuation of our house. This was due to the Australian stock market suffering a dip during November (but this has already been largely recouped during the first week of December). My SMSF account actually increased during November despite there being no employer contributions deposited during the month and the drop in the local stock market. This was because our investment in Vanguard LifeStrategy HighGrowth Index fund gained value, probably due largely to the drop in the Aussie dollar pushing up the value of unhedged overseas investments.

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